What it does
Level Up is an activated ability (from the Rise of the Eldrazi set) that lets you pay a cost, written as a mana symbol, to put a level counter on the creature. As the creature accumulates level counters, it crosses thresholds printed on its card, gaining bigger power/toughness and new abilities. You can only activate Level Up at sorcery speed (your main phase, empty stack), but you can activate it multiple times in one turn if you have the mana.
The most common misunderstanding: level counters never go away on their own and the creature stays "leveled up" permanently—but if it leaves the battlefield, the counters are lost, resetting it. Also, the printed base power/toughness only applies at level 0; once it's in a higher level band, that band's stats override the base.
In Commander, Level Up creatures are mana sinks that reward going long, making them solid in slower, grindy decks where excess mana would otherwise be wasted.













