There is a concept that a having immediate effect on the game or creating an effect that may be triggered/used later (no, effect of Dragon's Desolation is not triggered) is necessary as necessary is meting playability conditions stated in text of a card.CRF, Clarifications and Rulings, Legal Play of Cards wrote:A player may not play a card just to discard it (i.e., just get it out of his or her hand).
Specifically, a card may only be declared if it meets at least one of the following
criteria:
• The card must have an immediate effect on the game.
• The card is a long-event. Long-events can always be played, even if ultimately
they will not affect play.
• The card has a potential effect on play that could be triggered later (e.g., the
second use of Dragon's Desolation). Most permanent-events fall into this
category. Only those that are playable on or with a certain entity are restrictive.
For example, you cannot play a corruption card if no character exists that would
be affected by it.
As though anyone could prove that between declaration and resolution of a given card situation will not change in such way that what appeared at declaration as a card having no immediate/could be used/triggered later effect will not have such effect at resolution.
Dark Minions: Exhalation of Decay
Rarity: Common, Precise: C2
Hazard: Short-event
Playable on an Undead hazard creature in your discard pile. If target Undead can attack, bring it into play as a creature that attacks immediately (not counting against the hazard limit). The attacks prowess is modified by -1. "...wavering and blowing like a noisome exhalation of decay, a corpse-light, a light the illuminated nothing."-LotRIV
Bold original.Dark Minions: In Great Wrath
Rarity: Uncommon, Precise: U2
Hazard: Short-event
Playable on a Nazgûl in your discard pile that could immediately attack. The Nazgûl attacks immediately (not counting against the hazard limit) with +2 prowess and -1 body. "...the noise of hoofs broke out, and gathering to a gallop, went hammering away into the darkness."-LotRI
Can someone prove that conditions that allow a target Undead to attack that did not exist at declaration may not appear at resolution?
Or maybe they must exist at declaration (and at resolution) and a difference between "Playable on X in your discard pile. If X can attack [...]" and
"Playable on X in your discard pile that could immediately attack. X attacks immediately [...]" is meaningless?