diff --git a/common/locales/en/api-v3.json b/common/locales/en/api-v3.json
index a9c0a0fb2d..0546d97789 100644
--- a/common/locales/en/api-v3.json
+++ b/common/locales/en/api-v3.json
@@ -128,5 +128,7 @@
   "privateMessageGiftSubscriptionMessage": "<%= numberOfMonths %> months of subscription! ",
   "cannotSendGemsToYourself": "Cannot send gems to yourself. Try a subscription instead.",
   "notEnoughGemsToSend": "Amount must be within 0 and your current number of gems.",
-  "mustPurchaseToSet": "Must purchase <%= val %> to set it on <%= key %>."
+  "mustPurchaseToSet": "Must purchase <%= val %> to set it on <%= key %>.",
+  "mysteryItemIsEmpty": "Mystery items are empty",
+  "mysteryItemOpened": "Mystery item opened."
 }
diff --git a/common/script/index.js b/common/script/index.js
index 7f9736044d..3d91749c62 100644
--- a/common/script/index.js
+++ b/common/script/index.js
@@ -114,6 +114,7 @@ import feed from './ops/feed';
 import equip from './ops/equip';
 import changeClass from './ops/changeClass';
 import disableClasses from './ops/disableClasses';
+import openMysteryItem from './ops/openMysteryItem';
 
 api.ops = {
   scoreTask,
@@ -129,6 +130,7 @@ api.ops = {
   equip,
   changeClass,
   disableClasses,
+  openMysteryItem,
 };
 
 import handleTwoHanded from './fns/handleTwoHanded';
diff --git a/common/script/ops/openMysteryItem.js b/common/script/ops/openMysteryItem.js
index eb28c605e0..5767ee5f75 100644
--- a/common/script/ops/openMysteryItem.js
+++ b/common/script/ops/openMysteryItem.js
@@ -1,32 +1,40 @@
 import content from '../content/index';
+import i18n from '../i18n';
+import {
+  BadRequest,
+} from '../libs/errors';
+import _ from 'lodash';
+
+module.exports = function openMysteryItem (user, req = {}, analytics) {
+  let item = user.purchased.plan.mysteryItems.shift();
 
-module.exports = function(user, req, cb, analytics) {
-  var analyticsData, item, ref, ref1;
-  item = (ref = user.purchased.plan) != null ? (ref1 = ref.mysteryItems) != null ? ref1.shift() : void 0 : void 0;
   if (!item) {
-    return typeof cb === "function" ? cb({
-      code: 400,
-      message: "Empty"
-    }) : void 0;
-  }
-  item = content.gear.flat[item];
-  user.items.gear.owned[item.key] = true;
-  if (typeof user.markModified === "function") {
-    user.markModified('purchased.plan.mysteryItems');
+    throw new BadRequest(i18n.t('mysteryItemIsEmpty', req.language));
   }
+
+  item = _.cloneDeep(content.gear.flat[item]);
   item.notificationType = 'Mystery';
-  analyticsData = {
-    uuid: user._id,
-    itemKey: item,
-    itemType: 'Subscriber Gear',
-    acquireMethod: 'Subscriber',
-    category: 'behavior'
-  };
-  if (analytics != null) {
-    analytics.track('open mystery item', analyticsData);
+  user.items.gear.owned[item.key] = true;
+
+  user.markModified('purchased.plan.mysteryItems');
+
+  if (analytics) {
+    analytics.track('open mystery item', {
+      uuid: user._id,
+      itemKey: item,
+      itemType: 'Subscriber Gear',
+      acquireMethod: 'Subscriber',
+      category: 'behavior',
+    });
   }
+
   if (typeof window !== 'undefined') {
-    (user._tmp != null ? user._tmp : user._tmp = {}).drop = item;
+    if (!user._tmp) user._tmp = {};
+    user._tmp.drop = item;
   }
-  return typeof cb === "function" ? cb(null, user.items.gear.owned) : void 0;
+
+  return {
+    message: i18n.t('mysteryItemOpened', req.language),
+    data: user.items.gear.owned,
+  };
 };
diff --git a/tasks/gulp-eslint.js b/tasks/gulp-eslint.js
index 6fb94f6d2b..3aa9f57c75 100644
--- a/tasks/gulp-eslint.js
+++ b/tasks/gulp-eslint.js
@@ -29,7 +29,6 @@ const COMMON_FILES = [
   '!./common/script/ops/getTag.js',
   '!./common/script/ops/getTags.js',
   '!./common/script/ops/hourglassPurchase.js',
-  '!./common/script/ops/openMysteryItem.js',
   '!./common/script/ops/purchase.js',
   '!./common/script/ops/readCard.js',
   '!./common/script/ops/rebirth.js',
diff --git a/test/api/v3/integration/user/POST-user_open_mystery_item.test.js b/test/api/v3/integration/user/POST-user_open_mystery_item.test.js
new file mode 100644
index 0000000000..2c43445118
--- /dev/null
+++ b/test/api/v3/integration/user/POST-user_open_mystery_item.test.js
@@ -0,0 +1,26 @@
+import {
+  generateUser,
+  translate as t,
+} from '../../../../helpers/api-integration/v3';
+
+describe('POST /user/open-mystery-item', () => {
+  let user;
+  let mysteryItemKey = 'eyewear_special_summerRogue';
+
+  beforeEach(async () => {
+    user = await generateUser({
+      'purchased.plan.mysteryItems': [mysteryItemKey],
+    });
+  });
+
+  // More tests in common code unit tests
+
+  it('opens a mystery item', async () => {
+    let response = await user.post(`/user/open-mystery-item`);
+    await user.sync();
+
+    expect(user.items.gear.owned[mysteryItemKey]).to.be.true;
+    expect(response.message).to.equal(t('mysteryItemOpened'));
+    expect(response.data).to.deep.equal(user.items.gear.owned);
+  });
+});
diff --git a/test/common/ops/openMysteryItem.js b/test/common/ops/openMysteryItem.js
new file mode 100644
index 0000000000..c45146a585
--- /dev/null
+++ b/test/common/ops/openMysteryItem.js
@@ -0,0 +1,38 @@
+import openMysteryItem from '../../../common/script/ops/openMysteryItem';
+import {
+  generateUser,
+} from '../../helpers/common.helper';
+import {
+  BadRequest,
+} from '../../../common/script/libs/errors';
+import i18n from '../../../common/script/i18n';
+
+describe('shared.ops.openMysteryItem', () => {
+  let user;
+
+  beforeEach(() => {
+    user = generateUser();
+  });
+
+  it('returns error when item key is empty', (done) => {
+    try {
+      openMysteryItem(user);
+    } catch (err) {
+      expect(err).to.be.an.instanceof(BadRequest);
+      expect(err.message).to.equal(i18n.t('mysteryItemIsEmpty'));
+      done();
+    }
+  });
+
+  it('opens mystery item', () => {
+    let mysteryItemKey = 'eyewear_special_summerRogue';
+
+    user.purchased.plan.mysteryItems = [mysteryItemKey];
+
+    let response = openMysteryItem(user);
+
+    expect(user.items.gear.owned[mysteryItemKey]).to.be.true;
+    expect(response.message).to.equal(i18n.t('mysteryItemOpened'));
+    expect(response.data).to.equal(user.items.gear.owned);
+  });
+});
diff --git a/website/src/controllers/api-v3/user.js b/website/src/controllers/api-v3/user.js
index 147f1552c9..a163bcdf34 100644
--- a/website/src/controllers/api-v3/user.js
+++ b/website/src/controllers/api-v3/user.js
@@ -676,4 +676,24 @@ api.disableClasses = {
   },
 };
 
+/**
+* @api {post} /user/open-mystery-item Open the mystery item.
+* @apiVersion 3.0.0
+* @apiName UserOpenMysteryItem
+* @apiGroup User
+*
+* @apiSuccess {Object} data `user.items.gear.owned`
+*/
+api.userOpenMysteryItem = {
+  method: 'POST',
+  middlewares: [authWithHeaders(), cron],
+  url: '/user/open-mystery-item',
+  async handler (req, res) {
+    let user = res.locals.user;
+    let openMysteryItemResponse = common.ops.openMysteryItem(user, req, res.analytics);
+    await user.save();
+    res.respond(200, openMysteryItemResponse);
+  },
+};
+
 module.exports = api;