If you activate the third ability, and the target creature is an illegal target when the ability tries to resolve, it won’t resolve and none of its effects will happen. You won’t gain any life.

The emblem is owned and controlled by the target of the ability that created it. In a multiplayer game, if Garruk’s owner leaves the game, the emblem does not.

The first ability can target and destroy a Garruk planeswalker controlled by another player.

The emblem’s ability won’t trigger if a creature attacks a planeswalker.