Choose for the build you have
Look for something that improves crowd clearing, boss damage or survival. If nothing fits, decide whether to reroll, skip or banish instead of simply taking the largest number.
Each action has a different cost
F does not grant an upgrade by itself; X gives no card effect; Z changes the remaining run’s choice pool. Confirm a choice with the mouse or keys 1–4.
The Lab can increase the number of uses and separately unlock a fourth upgrade choice.