Sentinel

Sentinel is a 1-Energy Ironclad skill that grants 5 Block (8 upgraded) and Exhausts. If you were attacked since your last turn, it additionally grants 3 Energy. When the Energy trigger fires, Sentinel is essentially a free 5 Block that also gives you 3 extra Energy — extraordinarily powerful. In fights where the enemy consistently attacks you, Sentinel is a reliable high-value play.

The Energy trigger makes Sentinel context-dependent but potentially the best 1-Energy card in the Ironclad's kit in the right situation. After being attacked, play Sentinel and immediately have 3 additional Energy to work with. Upgraded at 8 Block, the baseline value improves significantly. A high pick in any Ironclad run that expects consistent incoming attacks.