To unlock the Til Death Do Us Part trophy in Devious Dungeon, you need to purchase at least one Ring from the main shop which can be found in the King's Hall upon death, or between every four levels during a run.
The cheapest ring is the Copper Ring which can be bought for 100 coins. You should get 100 coins pretty quickly in the game by just smashing open every crate and object that you see, as well as defeating all enemies in a level. Once you have bought the cheapest ring the Til Death Do Us Part trophy will unlock.