In-deck effect

In-deck effects are card effects that are active or that activate while they are in the player's deck, rather than while in the battlefield. Along with in-hand effects, in-deck effects are notable for being exceptions to the general game rule that cards do not become active until played or otherwise put into play.

The only current in-deck effects are triggered effects, including one that triggers at the start of the game.

Quests have the effect of guaranteeing themselves as part of the starting mulligan if one is in a player's 30 card deck, but this is more of a special mulligan rule than an in-deck effect.