Ability

An ability is the special game text a card contributes to the game.

Unless an ability explicitly references an out-of-play area (such as a hand, deck, archives, or discard pile), that ability can only interact with cards that are in play. Abilities that interact with a card after it is destroyed can interact with that card while it is in an out-of-play zone that is not hidden.

Abilities on a creature, artifact, or upgrade are only active (and can only be resolved) while that card is in play, unless the ability explicitly references being used from an out-of-play area. Once an ability on a card has started to resolve, that ability will finish resolving even if the card leaves play.

If resolving part of the instructions of a card ability causes other card effects to begin to resolve, resolve those other card effects before continuing to resolve the instructions of the first card.

Related Topics: Cannot, Constant Abilities, Destroyed, Enters Play, Leaves Play, "Play" Abilities, Out-of-Play Zones

—KeyForge Master Rulebook v17.4 September 2024

Commentary

There are currently no cards that force the non-active player to make any decisions. According to FFG, "The 'unless otherwise specified' language of card abilities was included more for future-proofing purposes in case there was a strange interaction between cards that would instruct the non-active player to make a decision."

Source

If a card ability allows a player to play or use another card (or to fight or to reap with a card), the chosen card may belong to any house unless the ability specifically states otherwise.

Source: Using Cards Via Other Abilities