Use

The active player can use any number of cards from the active house that they have in play during step three of their turn. Depending on a card’s type, the active player is able to do different things when using that card.

See Using Artifacts or Using Creatures. Actions and Upgrades are not considered to be "used".

—KeyForge Master Rulebook v17.3 March 2024

Commentary

Any time a stunned creature could normally be used, it can instead be used by exhausting it to remove its stun status card. If a card effect would cause a stunned creature to fight, reap, or use an action or omni ability, instead that creature is exhausted and the stun status card is removed. This is considered "using" that creature.

Source: Stun