diff --git a/app/imports/api/engine/action/applyProperties/applyActionProperty.test.ts b/app/imports/api/engine/action/applyProperties/applyActionProperty.test.ts
index f47ac14b..8a5ba16b 100644
--- a/app/imports/api/engine/action/applyProperties/applyActionProperty.test.ts
+++ b/app/imports/api/engine/action/applyProperties/applyActionProperty.test.ts
@@ -1,11 +1,13 @@
 import { assert } from 'chai';
 import {
   allMutations,
+  allUpdates,
   createTestCreature,
   randomIds,
   removeAllCreaturesAndProps,
   runActionById
 } from '/imports/api/engine/action/functions/actionEngineTest.testFn';
+import { Mutation, Update } from '/imports/api/engine/action/tasks/TaskResult';
 
 const [
   creatureId, targetCreatureId, targetCreature2Id,
@@ -30,7 +32,7 @@ const actionTestCreature = {
     {
       _id: attackMissId,
       type: 'action',
-      attackRoll: { calculation: '-20' },
+      attackRoll: { calculation: '-5' },
     },
     // Disable crits
     {
@@ -105,48 +107,57 @@ describe('Apply Action Properties', function () {
       targetCreatureId,
       targetCreature2Id,
     ]);
-    assert.deepEqual(allMutations(action), [{
-      contents: [{
-        name: 'Action'
-      }],
-      targetIds: [
-        targetCreatureId,
-        targetCreature2Id,
-      ]
-    }, {
-      contents: [{
-        inline: true,
-        name: 'Hit!',
-        value: '1d20 [10] + 10\n**20**',
-      }],
-      targetIds: [targetCreatureId],
-    }, {
-      contents: [{
-        inline: true,
-        name: 'Hit!',
-        value: '1d20 [10] + 10\n**20**',
-      }],
-      targetIds: [targetCreature2Id],
-    }]);
+    const expectedMutations: Mutation[] = [
+      {
+        contents: [{ name: 'Action' }],
+        targetIds: [targetCreatureId, targetCreature2Id]
+      }, {
+        contents: [{
+          inline: true,
+          name: 'Hit!',
+          value: '1d20 [10] + 10\n**20**',
+        }],
+        targetIds: [targetCreatureId],
+      }, {
+        contents: [{
+          inline: true,
+          name: 'Hit!',
+          value: '1d20 [10] + 10\n**20**',
+        }],
+        targetIds: [targetCreature2Id],
+      },
+    ];
+    assert.deepEqual(allMutations(action), expectedMutations);
+  });
+
+  it('should make attack rolls that use uses', async function () {
+    const action = await runActionById(usesActionId, [targetCreatureId]);
+    const expectedUpdates: Update[] = [
+      {
+        propId: usesActionId,
+        type: 'action',
+        inc: { usesUsed: 1, usesLeft: -1 },
+      }
+    ]
+    assert.deepEqual(allUpdates(action), expectedUpdates);
   });
 
   it('should make attack rolls that miss', async function () {
     const action = await runActionById(attackMissId, [targetCreatureId]);
-    assert.deepEqual(allMutations(action), [{
-      contents: [{
-        name: 'Action'
-      }],
-      targetIds: [
-        targetCreatureId,
-      ]
-    }, {
-      contents: [{
-        inline: true,
-        name: 'Miss!',
-        value: '1d20 [10] + 10\n**20**',
-      }],
-      targetIds: [targetCreatureId],
-    }]);
+    const expectedMutations: Mutation[] = [
+      {
+        contents: [{ name: 'Action' }],
+        targetIds: [targetCreatureId],
+      }, {
+        contents: [{
+          inline: true,
+          name: 'Miss!',
+          value: '1d20 [10] − 5\n**5**', // DiceCloud uses unicode minus
+        }],
+        targetIds: [targetCreatureId],
+      }
+    ];
+    assert.deepEqual(allMutations(action), expectedMutations);
   });
 
 });
diff --git a/app/imports/api/engine/action/applyProperties/applyActionProperty.ts b/app/imports/api/engine/action/applyProperties/applyActionProperty.ts
index 7a3c51a6..93ca5e09 100644
--- a/app/imports/api/engine/action/applyProperties/applyActionProperty.ts
+++ b/app/imports/api/engine/action/applyProperties/applyActionProperty.ts
@@ -10,11 +10,12 @@ import { applyAfterChildrenTriggers, applyAfterTriggers, applyChildren } from '/
 import recalculateCalculation from '/imports/api/engine/action/functions/recalculateCalculation';
 import { getEffectiveActionScope } from '/imports/api/engine/action/functions/getEffectiveActionScope';
 import numberToSignedString from '/imports/api/utility/numberToSignedString';
-import rollDice from '/imports/parser/rollDice';
-import { getFromScope, getNumberFromScope } from '/imports/api/creature/creatures/CreatureVariables';
+import { getNumberFromScope } from '/imports/api/creature/creatures/CreatureVariables';
+import InputProvider from '/imports/api/engine/action/functions/InputProvider';
+import { CalculatedField } from '/imports/api/properties/subSchemas/computedField';
 
 export default async function applyActionProperty(
-  task: PropTask, action: EngineAction, result: TaskResult, userInput
+  task: PropTask, action: EngineAction, result: TaskResult, userInput: InputProvider
 ): Promise<void> {
   const prop = task.prop;
   const targetIds = prop.target === 'self' ? [action.creatureId] : task.targetIds;
@@ -48,13 +49,13 @@ export default async function applyActionProperty(
 
   spendResources(action, prop, targetIds, result, userInput);
 
-  const attack = prop.attackRoll || prop.attackRollBonus;
+  const attack: CalculatedField = prop.attackRoll || prop.attackRollBonus;
 
   // Attack if there is an attack roll
   if (attack && attack.calculation) {
     if (targetIds.length) {
       for (const targetId of targetIds) {
-        await applyAttackToTarget(task, action, attack, targetId, result);
+        await applyAttackToTarget(task, action, attack, targetId, result, userInput);
         await applyAfterTriggers(action, prop, [targetId], userInput);
         await applyChildren(action, prop, [targetId], userInput);
       }
@@ -76,7 +77,8 @@ export default async function applyActionProperty(
 }
 
 async function applyAttackToTarget(
-  task: PropTask, action: EngineAction, attack, targetId, taskResult: TaskResult
+  task: PropTask, action: EngineAction, attack: CalculatedField, targetId: string,
+  taskResult: TaskResult, userInput: InputProvider
 ) {
   taskResult.pushScope = {
     '~attackHit': {},
@@ -86,7 +88,7 @@ async function applyAttackToTarget(
     '~attackRoll': {},
   }
 
-  await recalculateCalculation(attack, action, 'reduce');
+  await recalculateCalculation(attack, action, 'reduce', userInput);
   const scope = await getEffectiveActionScope(action);
   const contents: LogContent[] = [];
 
@@ -95,7 +97,7 @@ async function applyAttackToTarget(
     result,
     criticalHit,
     criticalMiss,
-  } = await rollAttack(attack, scope, taskResult.pushScope);
+  } = await rollAttack(attack, scope, taskResult.pushScope, userInput);
 
   const targetScope = getVariables(targetId);
   const targetArmor = getNumberFromScope('armor', targetScope)
@@ -143,7 +145,7 @@ async function applyAttackToTarget(
   }
 }
 
-async function applyAttackWithoutTarget(action, prop, attack, taskResult: TaskResult, userInput) {
+async function applyAttackWithoutTarget(action, prop, attack, taskResult: TaskResult, userInput: InputProvider) {
   taskResult.pushScope = {
     '~attackHit': {},
     '~attackMiss': {},
@@ -151,14 +153,14 @@ async function applyAttackWithoutTarget(action, prop, attack, taskResult: TaskRe
     '~criticalMiss': {},
     '~attackRoll': {},
   }
-  await recalculateCalculation(attack, action, 'reduce');
+  await recalculateCalculation(attack, action, 'reduce', userInput);
   const scope = await getEffectiveActionScope(action);
   const {
     resultPrefix,
     result,
     criticalHit,
     criticalMiss,
-  } = await rollAttack(attack, scope, taskResult.pushScope);
+  } = await rollAttack(attack, scope, taskResult.pushScope, userInput);
   let name = criticalHit ? 'Critical Hit!' : criticalMiss ? 'Critical Miss!' : 'To Hit';
   if (scope['~attackAdvantage']?.value === 1) {
     name += ' (Advantage)';
@@ -182,11 +184,11 @@ async function applyAttackWithoutTarget(action, prop, attack, taskResult: TaskRe
   });
 }
 
-async function rollAttack(attack, scope, resultPushScope) {
+async function rollAttack(attack, scope, resultPushScope, userInput: InputProvider) {
   const rollModifierText = numberToSignedString(attack.value, true);
   let value, resultPrefix;
   if (scope['~attackAdvantage']?.value === 1) {
-    const [a, b] = await rollDice(2, 20);
+    const [[a, b]] = await userInput.rollDice(attack, [{ number: 2, diceSize: 20 }]);
     if (a >= b) {
       value = a;
       resultPrefix = `1d20 [ ${a}, ~~${b}~~ ] ${rollModifierText}`;
@@ -195,7 +197,7 @@ async function rollAttack(attack, scope, resultPushScope) {
       resultPrefix = `1d20 [ ~~${a}~~, ${b} ] ${rollModifierText}`;
     }
   } else if (scope['~attackAdvantage']?.value === -1) {
-    const [a, b] = await rollDice(2, 20);
+    const [[a, b]] = await userInput.rollDice(attack, [{ number: 2, diceSize: 20 }]);
     if (a <= b) {
       value = a;
       resultPrefix = `1d20 [ ${a}, ~~${b}~~ ] ${rollModifierText}`;
@@ -204,7 +206,7 @@ async function rollAttack(attack, scope, resultPushScope) {
       resultPrefix = `1d20 [ ~~${a}~~, ${b} ] ${rollModifierText}`;
     }
   } else {
-    value = await rollDice(1, 20)[0];
+    [[value]] = await userInput.rollDice(attack, [{ number: 1, diceSize: 20 }]);
     resultPrefix = `1d20 [${value}] ${rollModifierText}`
   }
   resultPushScope['~attackDiceRoll'] = { value };
@@ -231,7 +233,7 @@ function applyCrits(value, scope, resultPushScope) {
   return { criticalHit, criticalMiss };
 }
 
-async function resetProperties(action: EngineAction, prop: any, result: TaskResult, userInput) {
+async function resetProperties(action: EngineAction, prop: any, result: TaskResult, userInput: InputProvider) {
   const attributes = getPropertiesOfType(action.creatureId, 'attribute');
   for (const att of attributes) {
     if (att.removed || att.inactive) continue;
diff --git a/app/imports/api/engine/action/applyProperties/applyAdjustmentProperty.ts b/app/imports/api/engine/action/applyProperties/applyAdjustmentProperty.ts
index c1b3ad20..b3ae201e 100644
--- a/app/imports/api/engine/action/applyProperties/applyAdjustmentProperty.ts
+++ b/app/imports/api/engine/action/applyProperties/applyAdjustmentProperty.ts
@@ -1,4 +1,5 @@
 import { EngineAction } from '/imports/api/engine/action/EngineActions';
+import InputProvider from '/imports/api/engine/action/functions/InputProvider';
 import { applyDefaultAfterPropTasks, applyTaskToEachTarget } from '/imports/api/engine/action/functions/applyTaskGroups';
 import recalculateCalculation from '/imports/api/engine/action/functions/recalculateCalculation';
 import { PropTask } from '/imports/api/engine/action/tasks/Task';
@@ -8,7 +9,7 @@ import { getSingleProperty, getVariables } from '/imports/api/engine/loadCreatur
 import getPropertyTitle from '/imports/api/utility/getPropertyTitle';
 
 export default async function applyAdjustmentProperty(
-  task: PropTask, action: EngineAction, result: TaskResult, userInput
+  task: PropTask, action: EngineAction, result: TaskResult, userInput: InputProvider
 ): Promise<void> {
   const prop = task.prop;
   const damageTargetIds = prop.target === 'self' ? [action.creatureId] : task.targetIds;
diff --git a/app/imports/api/engine/action/applyProperties/applyBranchProperty.ts b/app/imports/api/engine/action/applyProperties/applyBranchProperty.ts
index 19af353d..d935ce08 100644
--- a/app/imports/api/engine/action/applyProperties/applyBranchProperty.ts
+++ b/app/imports/api/engine/action/applyProperties/applyBranchProperty.ts
@@ -1,4 +1,5 @@
 import { EngineAction } from '/imports/api/engine/action/EngineActions';
+import InputProvider from '/imports/api/engine/action/functions/InputProvider';
 import { applyAfterPropTasksForSingleChild, applyAfterTasksSkipChildren, applyDefaultAfterPropTasks, applyTaskToEachTarget } from '/imports/api/engine/action/functions/applyTaskGroups';
 import { getEffectiveActionScope } from '/imports/api/engine/action/functions/getEffectiveActionScope';
 import recalculateCalculation from '/imports/api/engine/action/functions/recalculateCalculation';
@@ -8,7 +9,7 @@ import { getPropertyChildren } from '/imports/api/engine/loadCreatures';
 import rollDice from '/imports/parser/rollDice';
 
 export default async function applyBranchProperty(
-  task: PropTask, action: EngineAction, result: TaskResult, userInput
+  task: PropTask, action: EngineAction, result: TaskResult, userInput: InputProvider
 ): Promise<void> {
   const prop = task.prop;
   const targets = task.targetIds;
diff --git a/app/imports/api/engine/action/applyProperties/applyBuffProperty.ts b/app/imports/api/engine/action/applyProperties/applyBuffProperty.ts
index 28a04efc..6dc5589f 100644
--- a/app/imports/api/engine/action/applyProperties/applyBuffProperty.ts
+++ b/app/imports/api/engine/action/applyProperties/applyBuffProperty.ts
@@ -16,9 +16,10 @@ import recalculateInlineCalculations from '/imports/api/engine/action/functions/
 import getPropertyTitle from '/imports/api/utility/getPropertyTitle';
 import INLINE_CALCULATION_REGEX from '/imports/constants/INLINE_CALCULTION_REGEX';
 import { applyAfterTasksSkipChildren } from '/imports/api/engine/action/functions/applyTaskGroups';
+import InputProvider from '/imports/api/engine/action/functions/InputProvider';
 
 export default async function applyBuffProperty(
-  task: PropTask, action: EngineAction, result: TaskResult, userInput
+  task: PropTask, action: EngineAction, result: TaskResult, userInput: InputProvider
 ) {
   const prop = EJSON.clone(task.prop);
   const targetIds = prop.target === 'self' ? [action.creatureId] : task.targetIds;
diff --git a/app/imports/api/engine/action/functions/InputProvider.ts b/app/imports/api/engine/action/functions/InputProvider.ts
new file mode 100644
index 00000000..23c704eb
--- /dev/null
+++ b/app/imports/api/engine/action/functions/InputProvider.ts
@@ -0,0 +1,9 @@
+import { EngineAction } from '/imports/api/engine/action/EngineActions';
+
+type InputProvider = {
+  rollDice(
+    action: EngineAction, dice: { number: number, diceSize: number }[]
+  ): Promise<number[][]>;
+}
+
+export default InputProvider;
\ No newline at end of file
diff --git a/app/imports/api/engine/action/functions/actionEngineTest.testFn.ts b/app/imports/api/engine/action/functions/actionEngineTest.testFn.ts
index cb2467a2..6288d629 100644
--- a/app/imports/api/engine/action/functions/actionEngineTest.testFn.ts
+++ b/app/imports/api/engine/action/functions/actionEngineTest.testFn.ts
@@ -1,4 +1,3 @@
-import { assert } from 'chai';
 import '/imports/api/simpleSchemaConfig.js';
 import CreatureProperties from '/imports/api/creature/creatureProperties/CreatureProperties';
 import { propsFromForest } from '/imports/api/properties/tests/propTestBuilder.testFn';
@@ -9,6 +8,7 @@ import { loadCreature } from '/imports/api/engine/loadCreatures';
 import EngineActions, { EngineAction } from '/imports/api/engine/action/EngineActions';
 import { applyAction } from '/imports/api/engine/action/functions/applyAction';
 import { LogContent, Mutation, Removal, Update } from '/imports/api/engine/action/tasks/TaskResult';
+import InputProvider from '/imports/api/engine/action/functions/InputProvider';
 
 /**
  * Removes all creatures, properties, and creatureVariable documents from the database
@@ -59,12 +59,12 @@ export const randomIds = new Array(100).fill(undefined).map(() => Random.id());
  * @param userInputFn A function that simulates user input
  * @returns The Engine Action with mutations resulting from running the action
  */
-export async function runActionById(propId, targetIds?, userInputFn = () => 0) {
+export async function runActionById(propId, targetIds?, userInput = testInputProvider) {
   const prop = await CreatureProperties.findOneAsync(propId);
   const actionId = await createAction(prop, targetIds);
   const action = await EngineActions.findOneAsync(actionId);
   if (!action) throw 'Action is expected to exist';
-  await applyAction(action, userInputFn, { simulate: true });
+  await applyAction(action, userInput, { simulate: true });
   return action;
 }
 
@@ -148,3 +148,25 @@ export function allLogContent(action: EngineAction) {
   });
   return contents;
 }
+
+const testInputProvider: InputProvider = {
+  /**
+   * For testing, randomness is hard to deal with
+   * rollDice function returns the average roll for every dice rolled
+   * [5d10, 1d4] => [[6,6,6,6,6], [3]]
+   */
+  async rollDice(action, dice) {
+    const result: number[][] = [];
+    for (const diceRoll of dice) {
+      const averageRoll = Math.round(diceRoll.diceSize / 2);
+      // Return an array full of averagely rolled dice
+      result.push(
+        new Array(diceRoll.number)
+          .fill(averageRoll)
+      )
+    }
+    return result;
+  }
+}
+
+export { testInputProvider }
\ No newline at end of file
diff --git a/app/imports/api/engine/action/functions/applyAction.ts b/app/imports/api/engine/action/functions/applyAction.ts
index ec811e22..1bb11a02 100644
--- a/app/imports/api/engine/action/functions/applyAction.ts
+++ b/app/imports/api/engine/action/functions/applyAction.ts
@@ -1,7 +1,8 @@
-import { EngineAction, ActionSchema } from '/imports/api/engine/action/EngineActions';
+import EngineActions, { EngineAction, ActionSchema } from '/imports/api/engine/action/EngineActions';
 import { getSingleProperty } from '/imports/api/engine/loadCreatures';
 import applyTask from '/imports/api/engine/action/tasks/applyTask'
 import { isEmpty } from 'lodash';
+import InputProvider from '/imports/api/engine/action/functions/InputProvider';
 
 // TODO create a function to get the effective value of a property,
 // simulating all the result updates in the action so far
@@ -10,12 +11,12 @@ import { isEmpty } from 'lodash';
 // This is run once as a simulation on the client awaiting all the various inputs or step through
 // clicks from the user, then it is run as part of the runAction method, where it is expected to
 // complete instantly on the client, and sent to the server as a method call
-export async function applyAction(action: EngineAction, userInput?: any[] | Function, options?: {
+export async function applyAction(action: EngineAction, userInput: InputProvider, options?: {
   simulate?: boolean, stepThrough?: boolean
 }) {
   const { simulate, stepThrough } = options || {};
   if (!simulate && stepThrough) throw 'Cannot step through unless simulating';
-  if (simulate && typeof userInput !== 'function') throw 'Must provide a function to get user input when simulating';
+  if (simulate && !userInput) throw 'Must provide a function to get user input when simulating';
 
   action._stepThrough = stepThrough;
   action._isSimulation = simulate;
@@ -37,6 +38,6 @@ function writeChangedAction(original: EngineAction, changed: EngineAction) {
     }
   }
   if (!isEmpty($set) && original._id) {
-    return Actions.updateAsync(original._id, { $set });
+    return EngineActions.updateAsync(original._id, { $set });
   }
 }
diff --git a/app/imports/api/engine/action/functions/recalculateCalculation.ts b/app/imports/api/engine/action/functions/recalculateCalculation.ts
index b8fb28ea..02588bcb 100644
--- a/app/imports/api/engine/action/functions/recalculateCalculation.ts
+++ b/app/imports/api/engine/action/functions/recalculateCalculation.ts
@@ -2,25 +2,33 @@ import { Context, toPrimitiveOrString } from '/imports/parser/resolve';
 import {
   aggregateCalculationEffects,
   aggregateCalculationProficiencies,
-  resolveCalculationNode,
 } from '/imports/api/engine/computation/computeComputation/computeByType/computeCalculation';
 import { getSingleProperty } from '/imports/api/engine/loadCreatures';
 import resolve from '/imports/parser/resolve';
 import { getEffectiveActionScope } from '/imports/api/engine/action/functions/getEffectiveActionScope';
+import { CalculatedField } from '/imports/api/properties/subSchemas/computedField';
+import { ResolveLevel } from '/imports/parser/parseTree/NodeFactory';
+import InputProvider from '/imports/api/engine/action/functions/InputProvider';
+import { EngineAction } from '/imports/api/engine/action/EngineActions';
 
 // TODO Redo the work of
 // imports/api/engine/computation/computeComputation/computeByType/computeCalculation.js
 // But in the action scope
 export default async function recalculateCalculation(
-  calcObj, action, parseLevel = 'reduce', context, scope
+  calcObj: CalculatedField,
+  action,
+  parseLevel: ResolveLevel = 'reduce',
+  userInput: InputProvider,
 ) {
   if (!calcObj?.parseNode) return;
-  calcObj._parseLevel = parseLevel;
-  if (!scope) {
-    scope = await getEffectiveActionScope(action);
-  }
-  // Re-resolve the parse node
-  resolveCalculationNode(calcObj, calcObj.parseNode, scope, context);
+  const scope = await getEffectiveActionScope(action);
+  // Re-resolve the parse node before effects and proficiencies
+  const {
+    result: unaffectedResult,
+    context
+  } = resolve(parseLevel, calcObj.parseNode, scope);
+  calcObj.valueNode = unaffectedResult;
+
   // store the unaffected value
   if (calcObj.effectIds || calcObj.proficiencyIds) {
     calcObj.unaffected = toPrimitiveOrString(calcObj.valueNode);
@@ -35,19 +43,28 @@ export default async function recalculateCalculation(
     id => getSingleProperty(action.creatureId, id),
     scope['proficiencyBonus']?.value || 0
   );
-  // Resolve the modified valueNode
-  resolveCalculationNode(calcObj, calcObj.valueNode, scope, context);
 
-  // Store the primitive value
-  calcObj.value = toPrimitiveOrString(calcObj.valueNode);
-  // TODO log errors
+  // Resolve the modified valueNode, use the same context
+  const {
+    result: finalResult
+  } = resolve(parseLevel, calcObj.parseNode, scope, context);
+
+  // Store the errors
+  calcObj.errors = context.errors;
+
+  // Store the value and its primitive
+  calcObj.value = toPrimitiveOrString(finalResult);
+  calcObj.valueNode = finalResult;
+
 }
 
-export async function rollAndReduceCalculation(calcObj, action) {
+export async function rollAndReduceCalculation(
+  calcObj: CalculatedField, action: EngineAction, userInput: InputProvider
+) {
   const context = new Context();
   const scope = await getEffectiveActionScope(action);
   // Compile
-  recalculateCalculation(calcObj, action, 'compile', context, scope);
+  recalculateCalculation(calcObj, action, 'compile', userInput);
   const compiled = calcObj.valueNode;
 
   // Roll
diff --git a/app/imports/api/engine/action/tasks/applyTask.ts b/app/imports/api/engine/action/tasks/applyTask.ts
index 6794f596..796d19e2 100644
--- a/app/imports/api/engine/action/tasks/applyTask.ts
+++ b/app/imports/api/engine/action/tasks/applyTask.ts
@@ -5,8 +5,11 @@ import applyDamagePropTask from '/imports/api/engine/action/tasks/applyDamagePro
 import applyItemAsAmmoTask from '/imports/api/engine/action/tasks/applyItemAsAmmoTask';
 import { getSingleProperty } from '/imports/api/engine/loadCreatures';
 import applyProperties from '/imports/api/engine/action/applyProperties';
+import InputProvider from '/imports/api/engine/action/functions/InputProvider';
 
-export default async function applyTask(action: EngineAction, task: Task, userInput?): Promise<void> {
+export default async function applyTask(
+  action: EngineAction, task: Task, userInput: InputProvider
+): Promise<void> {
   action.taskCount += 1;
   if (action.taskCount > 100) throw 'Only 100 properties can be applied at once';
 
diff --git a/app/imports/api/properties/subSchemas/computedField.ts b/app/imports/api/properties/subSchemas/computedField.ts
index cba0c0da..515613e1 100644
--- a/app/imports/api/properties/subSchemas/computedField.ts
+++ b/app/imports/api/properties/subSchemas/computedField.ts
@@ -1,15 +1,20 @@
 import SimpleSchema from 'simpl-schema';
 import ErrorSchema from '/imports/api/properties/subSchemas/ErrorSchema';
 import STORAGE_LIMITS from '/imports/constants/STORAGE_LIMITS';
+import ParseNode from '/imports/parser/parseTree/ParseNode';
+import { ConstantValueType } from '/imports/parser/parseTree/constant';
 
 export interface CalculatedField {
-  calculation?: string,
-  value?: string | number,
-  effectIds?: string[],
-  parseNode?: any,
-  parseError?: any,
-  hash?: number,
-  errors?: any[],
+  calculation?: string;
+  value?: ConstantValueType;
+  valueNode: ParseNode;
+  effectIds?: string[];
+  proficiencyIds?: string[];
+  unaffected?: ConstantValueType;
+  parseNode?: ParseNode;
+  parseError?: any;
+  hash?: number;
+  errors?: any[];
 }
 
 // Get schemas that apply fields directly so they can be gracefully extended
diff --git a/app/imports/parser/parseTree/constant.ts b/app/imports/parser/parseTree/constant.ts
index 23c2db8c..e74a6397 100644
--- a/app/imports/parser/parseTree/constant.ts
+++ b/app/imports/parser/parseTree/constant.ts
@@ -1,7 +1,7 @@
 import NodeFactory from '/imports/parser/parseTree/NodeFactory';
 import { Context, ResolvedResult } from '/imports/parser/resolve';
 
-type ConstantValueType = number | string | boolean | undefined
+export type ConstantValueType = number | string | boolean | undefined
 
 export type ConstantNode = {
   parseType: 'constant';
diff --git a/app/imports/parser/resolve.ts b/app/imports/parser/resolve.ts
index 7d25bbb7..a97deb72 100644
--- a/app/imports/parser/resolve.ts
+++ b/app/imports/parser/resolve.ts
@@ -1,5 +1,6 @@
 import nodeTypeIndex from './parseTree/_index';
 import ParseNode from '/imports/parser/parseTree/ParseNode';
+import { ConstantValueType } from '/imports/parser/parseTree/constant';
 
 // Takes a parse node and computes it to a set detail level
 // returns {result, context}
@@ -37,10 +38,10 @@ export function toString(node: ParseNode) {
   return type.toString(node);
 }
 
-export function toPrimitiveOrString(node) {
+export function toPrimitiveOrString(node: ParseNode): ConstantValueType {
   if (!node) return '';
   if (node.parseType === 'constant') return node.value;
-  if (node.parseType === 'error') return null;
+  if (node.parseType === 'error') return undefined;
   return toString(node);
 }
 
diff --git a/app/imports/parser/rollDice.js b/app/imports/parser/rollDice.js
deleted file mode 100644
index 4e379ba6..00000000
--- a/app/imports/parser/rollDice.js
+++ /dev/null
@@ -1,9 +0,0 @@
-export default function rollDice(number, diceSize){
-  let values = [];
-  let randomSrc = DDP.randomStream('diceRoller');
-  for (let i = 0; i < number; i++){
-    let roll = ~~(randomSrc.fraction() * diceSize) + 1
-    values.push(roll);
-  }
-  return values;
-}
diff --git a/app/imports/parser/rollDice.ts b/app/imports/parser/rollDice.ts
new file mode 100644
index 00000000..df353c03
--- /dev/null
+++ b/app/imports/parser/rollDice.ts
@@ -0,0 +1,12 @@
+export default function rollDice(number: number, diceSize: number): number[] {
+  const values: number[] = [];
+  const randomSrc = DDP.randomStream('diceRoller');
+  if (number > 100) {
+    throw new Meteor.Error('Too many dice', 'can only roll up to 100 dice at once');
+  }
+  for (let i = 0; i < number; i++) {
+    const roll = ~~(randomSrc.fraction() * diceSize) + 1
+    values.push(roll);
+  }
+  return values;
+}