Kicker is an additional cost that you may pay while casting a spell to make that spell more powerful. A kicked spell might gain an additional effect, produce more targets, or transform an ordinary card into a much larger late-game play.
Thornscape Battlemage demonstrates kicker with multiple optional bonuses, while Verazol, the Split Current can copy kicked spells. Multikicker allows the additional cost to be paid any number of times for effects that scale accordingly.
