Attach to a hero. Restricted.
Attached hero gets +4 Hit Points.
Denethor, The Return of the King
Core Set #40. Tactics.
Citadel Plate is kind of expensive, but it's effect is unequaled. It's one of only 11 HP boosting player cards and the only one that does not require a specific trait or something like that. Granted, it's restricted and that limits it's use, but seriously? Four HP? yes please!