In update 0.38 (which is coming very soon!), we have made changes to Dungeon Marks:
‘Dungeon Marks’ will now be referred to just as ‘Marks’.
Marks have been removed from Dungeon Rewards.
The ability to Empower Dungeons for extra rewards has therefore also been removed.
As well as the ability to upgrade your Marks for lower tier Marks has also been removed.
Marks can now be earned from Events.
Marks will be used to purchase items from the Event Shops.
This is important; As you will no longer be able to purchase Chests using Marks in update 0.38, if you wanted to spend your Marks on Chests or upgrade your existing Marks, please do so as soon as possible.