Bash

Bash is the Ironclad's third starter card, costing 2 Energy to deal 8 damage and apply 2 Vulnerable (10 damage and 3 Vulnerable when upgraded). Vulnerable makes enemies take 50% more damage from attacks, so Bash effectively sets up all your subsequent attacks in that turn and the next. Even at 2 Energy, the damage amplification it provides for your other attacks makes it well worth its cost in the early game.

Bash is strongest when you have multiple attacks to follow it up with — a turn where you play Bash into two Strikes deals significantly more total damage than playing the same cards without Vulnerable. It synergizes naturally with Strength-stacking builds and multi-hit attacks. Upgrading Bash from 2 to 3 Vulnerable stacks is a meaningful improvement, as it doubles the Vulnerable duration and lets you get more turns of amplified damage. Later in a run, Bash often gets replaced by more efficient openers, but in Act 1 it does real work.