Initial

module/data/action/baseAction.mjs

@@ -376,6 +376,15 @@ export default class DHBaseAction extends ActionMixin(foundry.abstract.DataModel
 
         return tags;
     }
+
+    static migrateData(source) {
+        if (source.damage?.parts && Array.isArray(source.damage.parts)) {
+            source.damage.parts = source.damage.parts.reduce((acc, part) => {
+                acc[part.applyTo] = part;
+                return acc;
+            }, {});
+        }
+    }
 }
 
 export class ResourceUpdateMap extends Map {

module/data/actor/character.mjs

@@ -704,7 +704,7 @@ export default class DhCharacter extends DhCreature {
             isReversed: true
         };
 
-        this.attack.damage.parts[0].value.custom.formula = `@prof${this.basicAttackDamageDice}${this.rules.attack.damage.bonus ? ` + ${this.rules.attack.damage.bonus}` : ''}`;
+        this.attack.damage.parts.hitPoints.value.custom.formula = `@prof${this.basicAttackDamageDice}${this.rules.attack.damage.bonus ? ` + ${this.rules.attack.damage.bonus}` : ''}`;
     }
 
     getRollData() {

module/data/fields/_module.mjs

@@ -1,4 +1,5 @@
 export { ActionCollection } from './actionField.mjs';
+export { default as CollectionField } from './collectionField.mjs';
 export { default as FormulaField } from './formulaField.mjs';
 export { default as ForeignDocumentUUIDField } from './foreignDocumentUUIDField.mjs';
 export { default as ForeignDocumentUUIDArrayField } from './foreignDocumentUUIDArrayField.mjs';

module/data/fields/action/damageField.mjs

@@ -1,5 +1,6 @@
 import FormulaField from '../formulaField.mjs';
 import { setsEqual } from '../../../helpers/utils.mjs';
+import CollectionField from '../collectionField.mjs';
 
 const fields = foundry.data.fields;
 
@@ -12,7 +13,7 @@ export default class DamageField extends fields.SchemaField {
     /** @inheritDoc */
     constructor(options, context = {}) {
         const damageFields = {
-            parts: new fields.ArrayField(new fields.EmbeddedDataField(DHDamageData)),
+            parts: new CollectionField(DHDamageData, { collectionClass: DamagePartsCollection }),
             includeBase: new fields.BooleanField({
                 initial: false,
                 label: 'DAGGERHEART.ACTIONS.Settings.includeBase.label'
@@ -300,3 +301,9 @@ export class DHDamageData extends DHResourceData {
         };
     }
 }
+
+class DamagePartsCollection extends foundry.utils.Collection {
+    get hitPoints() {
+        return this.get('hitPoints');
+    }
+}

module/data/fields/collectionField.mjs

@@ -0,0 +1,25 @@
+export default class CollectionField extends foundry.data.fields.TypedObjectField {
+    constructor(model, options = { collectionClass: foundry.utils.Collection }, context = {}) {
+        super(new foundry.data.fields.EmbeddedDataField(model), options, context);
+        this.#elementClass = model;
+        this.#collectionClass = options.collectionClass;
+    }
+
+    /**
+     * The collection class
+     */
+    #collectionClass;
+
+    /**
+     * The collection element class.
+     */
+    #elementClass;
+
+    initialize(value, model, _options = {}) {
+        console.log(model);
+        const collection = new this.#collectionClass(
+            Object.entries(value).map(([key, value]) => [key, new this.#elementClass(value)])
+        );
+        return collection;
+    }
+}