diff --git a/.vscode/settings.json b/.vscode/settings.json
index 81f51528..dfc0d6d0 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -1,5 +1,6 @@
 {
   "cSpell.words": [
+    "alea",
     "autorun",
     "blackbox",
     "Crits",
diff --git a/app/imports/api/creature/creatureProperties/CreatureProperties.ts b/app/imports/api/creature/creatureProperties/CreatureProperties.ts
index e5c2c3a9..fcf8d490 100644
--- a/app/imports/api/creature/creatureProperties/CreatureProperties.ts
+++ b/app/imports/api/creature/creatureProperties/CreatureProperties.ts
@@ -7,12 +7,12 @@ import propertySchemasIndex from '/imports/api/properties/computedPropertySchema
 import { storedIconsSchema } from '/imports/api/icons/Icons';
 import STORAGE_LIMITS from '/imports/constants/STORAGE_LIMITS';
 
-const CreatureProperties: Mongo.Collection<CreatureProperty> = new Mongo.Collection('creatureProperties');
+// TODO make this a union type of all CreatureProperty types
+const CreatureProperties: Mongo.Collection<any> = new Mongo.Collection('creatureProperties');
 
-export interface CreatureProperty extends TreeDoc {
+export interface CreatureProperty {
   _id: string
   _migrationError?: string
-  type: string
   tags: string[]
   disabled?: boolean
   icon?: {
diff --git a/app/imports/api/engine/action/ActionEngine.test.ts b/app/imports/api/engine/action/ActionEngine.test.ts
index 84a42c7d..2c6fef7a 100644
--- a/app/imports/api/engine/action/ActionEngine.test.ts
+++ b/app/imports/api/engine/action/ActionEngine.test.ts
@@ -9,6 +9,7 @@ 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, Removal, Update } from '/imports/api/engine/action/tasks/TaskResult';
+import inputProvider from '/imports/api/engine/action/functions/inputProviderForTests.testFn';
 
 const creatureId = Random.id();
 const targetId = Random.id();
@@ -81,11 +82,12 @@ describe('Interrupt action system', function () {
       [{ value: 'child 2 of index branch' }]
     );
   });
-  it('Halts execution of choice branches', async function () {
-    let userInputRequested = false;
-    const requestUserInput = () => { userInputRequested = true; return 0 };
-    await runActionById(choiceBranchId, requestUserInput);
-    assert.isTrue(userInputRequested, 'User input should be requested when a choice branch is applied');
+  it('Gets choices from choice branches', async function () {
+    const action = await runActionById(choiceBranchId);
+    assert.deepEqual(
+      allLogContent(action),
+      [{ value: 'child 1 of choice branch' }]
+    );
   });
   it('Applies adjustments', async function () {
     let action = await runActionById(adjustmentSetId);
@@ -205,12 +207,12 @@ function createAction(prop, targetIds?) {
   return EngineActions.insertAsync(action);
 }
 
-async function runActionById(propId, userInputFn = () => 0) {
+async function runActionById(propId) {
   const prop = await CreatureProperties.findOneAsync(propId);
   const actionId = await createAction(prop);
   const action = await EngineActions.findOneAsync(actionId);
   if (!action) throw 'Action is expected to exist';
-  await applyAction(action, userInputFn, { simulate: true });
+  await applyAction(action, inputProvider, { simulate: true });
   return action;
 }
 
diff --git a/app/imports/api/engine/action/applyProperties/applyActionProperty.test.ts b/app/imports/api/engine/action/applyProperties/applyActionProperty.test.ts
index 8a5ba16b..a6785ef0 100644
--- a/app/imports/api/engine/action/applyProperties/applyActionProperty.test.ts
+++ b/app/imports/api/engine/action/applyProperties/applyActionProperty.test.ts
@@ -8,6 +8,7 @@ import {
   runActionById
 } from '/imports/api/engine/action/functions/actionEngineTest.testFn';
 import { Mutation, Update } from '/imports/api/engine/action/tasks/TaskResult';
+import Alea from 'alea';
 
 const [
   creatureId, targetCreatureId, targetCreature2Id,
@@ -93,6 +94,14 @@ describe('Apply Action Properties', function () {
     await createTestCreature(actionTargetCreature2);
   });
 
+  it('should generate random numbers reliably given consistent seeds', function () {
+    const aleaFraction = Alea('test', 'seeds');
+    const randomNumbers = [aleaFraction(), aleaFraction(), aleaFraction()];
+    assert.deepEqual(randomNumbers, [
+      0.19889510236680508, 0.9176857066340744, 0.042551583144813776
+    ]);
+  });
+
   it('should run empty actions', async function () {
     const action = await runActionById(emptyActionId);
     assert.exists(action);
diff --git a/app/imports/api/engine/action/applyProperties/applyAdjustmentProperty.ts b/app/imports/api/engine/action/applyProperties/applyAdjustmentProperty.ts
index b3ae201e..09f38171 100644
--- a/app/imports/api/engine/action/applyProperties/applyAdjustmentProperty.ts
+++ b/app/imports/api/engine/action/applyProperties/applyAdjustmentProperty.ts
@@ -24,7 +24,7 @@ export default async function applyAdjustmentProperty(
   }
 
   // Evaluate the amount
-  await recalculateCalculation(prop.amount, action, 'reduce');
+  await recalculateCalculation(prop.amount, action, 'reduce', userInput);
   const value = +prop.amount.value;
   if (!isFinite(value)) {
     return;
diff --git a/app/imports/api/engine/action/applyProperties/applyBranchProperty.ts b/app/imports/api/engine/action/applyProperties/applyBranchProperty.ts
index d935ce08..b12c93bb 100644
--- a/app/imports/api/engine/action/applyProperties/applyBranchProperty.ts
+++ b/app/imports/api/engine/action/applyProperties/applyBranchProperty.ts
@@ -1,6 +1,7 @@
+import { filter } from 'lodash';
 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 { applyAfterPropTasksForSingleChild, applyAfterPropTasksForSomeChildren, 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';
 import { PropTask } from '/imports/api/engine/action/tasks/Task';
@@ -16,7 +17,7 @@ export default async function applyBranchProperty(
 
   switch (prop.branchType) {
     case 'if': {
-      await recalculateCalculation(prop.condition, action, 'reduce');
+      await recalculateCalculation(prop.condition, action, 'reduce', userInput);
       if (prop.condition?.value) {
         return applyDefaultAfterPropTasks(action, prop, targets, userInput);
       } else {
@@ -28,7 +29,7 @@ export default async function applyBranchProperty(
       if (!children.length) {
         return applyAfterTasksSkipChildren(action, prop, targets, userInput);
       }
-      await recalculateCalculation(prop.condition, action, 'reduce');
+      await recalculateCalculation(prop.condition, action, 'reduce', userInput);
       if (!isFinite(prop.condition?.value)) {
         result.appendLog({
           name: 'Branch Error',
@@ -110,21 +111,17 @@ export default async function applyBranchProperty(
       }
       return applyDefaultAfterPropTasks(action, prop, targets, userInput);
     case 'choice': {
-      let index;
-      if (action._isSimulation) {
-        index = await userInput(prop);
-      } else {
-        // TODO
-        throw 'Reading stored user input not implemented'
-      }
       const children = await getPropertyChildren(action.creatureId, prop);
-      if (!children.length) {
+      let choices: string[];
+      let chosenChildren: typeof children = [];
+      if (children.length) {
+        choices = await userInput.choose(action, children);
+        chosenChildren = filter(children, child => choices.includes(child._id));
+      }
+      if (!children.length || !chosenChildren.length) {
         return applyAfterTasksSkipChildren(action, prop, targets, userInput);
       }
-      if (!isFinite(index) || index < 0) index = 0;
-      if (index > children.length - 1) index = children.length - 1;
-      const child = children[index];
-      return applyAfterPropTasksForSingleChild(action, prop, child, targets, userInput);
+      return applyAfterPropTasksForSomeChildren(action, prop, chosenChildren, targets, userInput);
     }
   }
 }
\ No newline at end of file
diff --git a/app/imports/api/engine/action/functions/InputProvider.ts b/app/imports/api/engine/action/functions/InputProvider.ts
index 23c704eb..f9c1933d 100644
--- a/app/imports/api/engine/action/functions/InputProvider.ts
+++ b/app/imports/api/engine/action/functions/InputProvider.ts
@@ -4,6 +4,17 @@ type InputProvider = {
   rollDice(
     action: EngineAction, dice: { number: number, diceSize: number }[]
   ): Promise<number[][]>;
+  /**
+   * Choose from a provided selection
+   * @param action 
+   * @param choices Options to choose from
+   * @param quantity Number of choices to make [min, max] inclusive, where -1 means no limit
+   */
+  choose(
+    action: EngineAction,
+    choices: ({ _id: string } & Record<string, any>)[],
+    quantity?: [min: number, max: number],
+  ): Promise<string[]>;
 }
 
 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 6288d629..1d5020d2 100644
--- a/app/imports/api/engine/action/functions/actionEngineTest.testFn.ts
+++ b/app/imports/api/engine/action/functions/actionEngineTest.testFn.ts
@@ -8,8 +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';
-
+import inputProvider from '/imports/api/engine/action/functions/inputProviderForTests.testFn';
 /**
  * Removes all creatures, properties, and creatureVariable documents from the database
  */
@@ -59,7 +58,7 @@ 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?, userInput = testInputProvider) {
+export async function runActionById(propId, targetIds?, userInput = inputProvider) {
   const prop = await CreatureProperties.findOneAsync(propId);
   const actionId = await createAction(prop, targetIds);
   const action = await EngineActions.findOneAsync(actionId);
@@ -148,25 +147,3 @@ 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/applyTaskGroups.ts b/app/imports/api/engine/action/functions/applyTaskGroups.ts
index 207ada37..2670453e 100644
--- a/app/imports/api/engine/action/functions/applyTaskGroups.ts
+++ b/app/imports/api/engine/action/functions/applyTaskGroups.ts
@@ -16,7 +16,6 @@ export async function applyChildren(
   action: EngineAction, prop, targetIds: string[], userInput
 ) {
   const children = await getPropertyChildren(action.creatureId, prop);
-  // Push the child tasks and related triggers to the stack
   for (const childProp of children) {
     await applyTask(action, { prop: childProp, targetIds }, userInput);
   }
@@ -101,6 +100,25 @@ export async function applyAfterPropTasksForSingleChild(
   await applyAfterChildrenTriggers(action, prop, targetIds, userInput);
 }
 
+/**
+ * Returns a list of tasks containing the following:
+ * After triggers
+ * After-children triggers
+ * @param action 
+ * @param prop 
+ * @param targetIds 
+ * @returns 
+ */
+export async function applyAfterPropTasksForSomeChildren(
+  action: EngineAction, prop, children, targetIds: string[], userInput
+) {
+  await applyAfterTriggers(action, prop, targetIds, userInput);
+  for (const childProp of children) {
+    await applyTask(action, { prop: childProp, targetIds }, userInput);
+  }
+  await applyAfterChildrenTriggers(action, prop, targetIds, userInput);
+}
+
 /**
  * Get all the trigger tasks for a given trigger path
  * @param action 
diff --git a/app/imports/api/engine/action/functions/inputProviderForTests.testFn.ts b/app/imports/api/engine/action/functions/inputProviderForTests.testFn.ts
new file mode 100644
index 00000000..c162f010
--- /dev/null
+++ b/app/imports/api/engine/action/functions/inputProviderForTests.testFn.ts
@@ -0,0 +1,34 @@
+import InputProvider from '/imports/api/engine/action/functions/InputProvider';
+
+const inputProviderForTests: 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;
+  },
+  /**
+   * For testing, always return the minimum number of choices, always choosing the first options
+   */
+  async choose(action, choices, quantity = [1, 1]) {
+    const chosen: string[] = [];
+    const choiceQuantity = quantity[0] <= 0 ? 1 : quantity[0];
+    for (let i = 0; i < choiceQuantity && i < choices.length; i += 1) {
+      chosen.push(choices[i]._id);
+    }
+    return chosen;
+  }
+}
+
+export default inputProviderForTests;
diff --git a/app/imports/api/properties/Actions.ts b/app/imports/api/properties/Actions.ts
index 0f7c6510..068db2a6 100644
--- a/app/imports/api/properties/Actions.ts
+++ b/app/imports/api/properties/Actions.ts
@@ -6,12 +6,24 @@ import VARIABLE_NAME_REGEX from '/imports/constants/VARIABLE_NAME_REGEX';
 import { CreatureProperty } from '/imports/api/creature/creatureProperties/CreatureProperties';
 import { InlineCalculation } from '/imports/api/properties/subSchemas/inlineCalculationField';
 import { CalculatedField } from '/imports/api/properties/subSchemas/computedField';
+import Property from '/imports/api/properties/Properties.type';
 
+export type CreatureAction = Action & CreatureProperty & {
+  overridden?: boolean
+  insufficientResources?: boolean
+}
+
+/*
+ * Actions are things a character can do
+ */
 export interface Action extends ActionBase {
   type: 'action'
 }
 
-export interface ActionBase extends CreatureProperty {
+/**
+ * Base property type for both spells and actions
+ */
+export interface ActionBase extends Property {
   name?: string
   summary?: InlineCalculation
   description?: InlineCalculation
@@ -23,9 +35,7 @@ export interface ActionBase extends CreatureProperty {
   usesUsed?: number
   reset?: string
   silent?: boolean
-  insufficientResources?: boolean
   usesLeft?: number
-  overridden?: boolean
   // Resources
   resources: {
     itemsConsumed: {
diff --git a/app/imports/api/properties/Attributes.js b/app/imports/api/properties/Attributes.ts
similarity index 77%
rename from app/imports/api/properties/Attributes.js
rename to app/imports/api/properties/Attributes.ts
index 0bac605a..d9d749c1 100644
--- a/app/imports/api/properties/Attributes.js
+++ b/app/imports/api/properties/Attributes.ts
@@ -2,11 +2,57 @@ import SimpleSchema from 'simpl-schema';
 import VARIABLE_NAME_REGEX from '/imports/constants/VARIABLE_NAME_REGEX';
 import STORAGE_LIMITS from '/imports/constants/STORAGE_LIMITS';
 import createPropertySchema from '/imports/api/properties/subSchemas/createPropertySchema';
+import { CreatureProperty } from '/imports/api/creature/creatureProperties/CreatureProperties';
+import { CalculatedField } from '/imports/api/properties/subSchemas/computedField';
+import { InlineCalculation } from '/imports/api/properties/subSchemas/inlineCalculationField';
+import { ConstantValueType } from '/imports/parser/parseTree/constant';
+import Property from '/imports/api/properties/Properties.type';
+
+export type CreatureAttribute = Attribute & CreatureProperty & {
+  total?: ConstantValueType;
+  value?: ConstantValueType;
+  modifier?: number;
+  proficiency?: 0 | 0.49 | 0.5 | 1 | 2;
+  advantage?: -1 | 0 | 1;
+  constitutionMod?: number;
+  hide?: true;
+  overridden?: true;
+  effectIds?: string[];
+  proficiencyIds?: string[];
+  definitions?: { _id: string, type: string, row?: number }[];
+}
+
+export interface Attribute extends Property {
+  type: 'attribute';
+  name?: string;
+  variableName?: string;
+  attributeType: 'ability' | 'stat' | 'modifier' | 'hitDice' | 'healthBar' | 'resource' |
+  'spellSlot' | 'utility';
+  hitDiceSize?: 'd1' | 'd2' | 'd4' | 'd6' | 'd8' | 'd10' | 'd12' | 'd20' | 'd100';
+  spellSlotLevel?: CalculatedField;
+  healthBarColorMid?: string;
+  healthBarColorLow?: string;
+  healthBarNoDamage?: true;
+  healthBarNoHealing?: true;
+  healthBarNoDamageOverflow?: true;
+  healthBarNoHealingOverflow?: true;
+  healthBarDamageOrder?: number;
+  healthBarHealingOrder?: number;
+  baseValue?: CalculatedField;
+  description?: InlineCalculation;
+  damage?: number;
+  decimal?: true;
+  ignoreLowerLimit?: true;
+  ignoreUpperLimit?: true;
+  hideWhenTotalZero?: true;
+  hideWhenValueZero?: true;
+  reset?: string;
+}
 
 /*
  * Attributes are numbered stats of a character
  */
-let AttributeSchema = createPropertySchema({
+const AttributeSchema = createPropertySchema({
   name: {
     type: String,
     optional: true,
@@ -134,7 +180,7 @@ let AttributeSchema = createPropertySchema({
   },
 });
 
-let ComputedOnlyAttributeSchema = createPropertySchema({
+const ComputedOnlyAttributeSchema = createPropertySchema({
   description: {
     type: 'computedOnlyInlineCalculationField',
     optional: true,
diff --git a/app/imports/api/properties/Properties.type.ts b/app/imports/api/properties/Properties.type.ts
new file mode 100644
index 00000000..e7aaa73f
--- /dev/null
+++ b/app/imports/api/properties/Properties.type.ts
@@ -0,0 +1,12 @@
+import { TreeDoc } from '/imports/api/parenting/ChildSchema';
+
+export default interface Property extends TreeDoc {
+  _id: string
+  _migrationError?: string
+  tags: string[]
+  icon?: {
+    name: string
+    shape: string
+  },
+  slotQuantityFilled?: number
+}
\ No newline at end of file
diff --git a/app/package-lock.json b/app/package-lock.json
index bbec14ff..5409c8fb 100644
--- a/app/package-lock.json
+++ b/app/package-lock.json
@@ -1790,6 +1790,11 @@
         "uri-js": "^4.2.2"
       }
     },
+    "alea": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/alea/-/alea-1.0.1.tgz",
+      "integrity": "sha512-QU+wv+ziDXaMxRdsQg/aH7sVfWdhKps5YP97IIwFkHCsbDZA3k87JXoZ5/iuemf4ntytzIWeScrRpae8+lDrXA=="
+    },
     "ansi-colors": {
       "version": "4.1.1",
       "resolved": "https://registry.npmjs.org/ansi-colors/-/ansi-colors-4.1.1.tgz",
diff --git a/app/package.json b/app/package.json
index a97a85c4..1dcad558 100644
--- a/app/package.json
+++ b/app/package.json
@@ -24,6 +24,7 @@
     "@chenfengyuan/vue-countdown": "^1.1.5",
     "@tozd/vue-observer-utils": "^0.5.0",
     "@types/meteor": "^2.9.8",
+    "alea": "^1.0.1",
     "aws-sdk": "^2.1559.0",
     "bcrypt": "^5.1.1",
     "chroma-js": "^2.4.2",