Defender
{2}: Golden Guardian fights another target creature you control. When Golden Guardian dies this turn, return it to the battlefield transformed under your control.
For more information on double-faced cards, see the Ixalan mechanics article (http://magic.wizards.com/en/articles/archive/feature/ixalan-mechanics).
If Golden Guardian leaves the battlefield before its activated ability has resolved, it won’t be returned to the battlefield when the ability resolves.
If the target of Golden Guardian’s activated ability isn’t a legal target as that ability resolves, or if Golden Guardian has left the battlefield, neither creature will deal or be dealt damage.
Once Golden Guardian’s activated ability has resolved, it will return to the battlefield transformed if it dies for any reason in that turn.