Bag of Preparation
Bag of Preparation is a common relic that draws 2 additional cards at the start of each combat, giving you a starting hand of 7 cards. This is a universal draw bonus that benefits every character and every deck archetype. Having more cards in your opening hand means more options, more likely access to key combo pieces, and a better chance of having both offense and defense available immediately.
The relic is straightforwardly powerful because card draw is one of the most valuable resources in the game. It helps thin-decked combo builds find their pieces, helps defensive builds find their block cards, and gives aggressive builds more attacks. Unlike the Silent's Ring of the Snake (which provides the same effect as a character perk), Bag of Preparation is a common relic available to all characters. The only marginal downside is that drawing 7 cards in a 5-card hand size can occasionally lead to awkward discards if your hand is full, though this is rarely a real issue.