Aiming for synergies can be a trap, though. Sometimes the correct pick is a bad card that has anti-synergy with your current deck, because it solves an immediate problem. For example, at the start of a run you generally should pick any attack better than a strike (almost all of them) even over super powerful late-game scaling cards and try to kill the Elites to get relics and build power.

After the first few runs through the Spire, you'll generally know what you will be facing, and what you need to do is pick cards that cover your bases against those potential upcoming fights.