702.154. Enlist

Enlist represents a static ability and a triggered ability. Enlist means “As this creature attacks, you may tap up to one untapped creature you control that you didn’t choose to attack with and that either has haste or has been under your control continuously since this turn began. When you do, this creature gets +X/+0 until end of turn, where X is the tapped creature’s power.”

Enlist’s static ability represents an optional cost to attack (see rule 508.1g). Its triggered ability is linked to that static ability (see rule 607.2h).

A creature “enlists” another creature when you pay the cost of the creature’s enlist ability by tapping the other creature. Note that it isn’t possible for a creature to enlist itself.

Multiple instances of enlist on a single creature function independently. The triggered ability represented by each instance of enlist triggers only once and only for the cost associated with that enlist ability.