Singing Bowl
Singing Bowl is an uncommon relic that gives you an additional option when presented with a card reward: instead of taking a card, you may instead gain 2 Max HP. This choice appears alongside the card options on every combat reward screen, allowing you to effectively convert any card reward into a permanent HP boost.
Singing Bowl is extremely powerful in lean, well-focused decks that don't want to add many cards. If your deck is already optimal and further card additions would hurt consistency, taking 2 Max HP from every reward is better than polluting your deck with mediocre cards. Over a full run with 15 to 20 card rewards, consistently choosing Max HP can add 30 to 40 or more HP to your maximum. Even in decks that want to add cards, the option gives you meaningful flexibility to skip bad rewards for HP rather than taking nothing.