I have added something like 15 relics into the game. They are powerful artifacts that changes the way the game works. From reviving on dead, gain more money for un-used gold cards on hand, to mana-shield to getting free-spin if you alter your decks a lot, to dealing extra damage on fully hp enemies.
These relics are rewards for player upon clearing the stage, and they will stay with you for the entire run. Now, upon choosing a stage, you can choose what artifact you want to have, as well as the stage-boss that you would be fight against.  This will make extra layers of fun and decision making into your run.

Add shop-reset and shop lock function. They are what they say, a way for you to reset the shop, or lock the content of the shop for next turn. But they cost money, so, think carefully before using them.