Metamorphic Alteration

If Metamorphic Alteration somehow enters the battlefield at the same time as another creature, it can't have the enchanted creature become a copy of that creature. You may choose only a creature that's already on the battlefield.

Metamorphic Alteration can cause a creature to become a copy of itself. This generally has no effect, but if that creature has a pair of linked abilities, the new abilities it has from the copy effect aren't linked to the abilities it had before.

If the chosen creature isn't normally a creature (for example, if the chosen creature is an animated Treetop Village), the enchanted creature becomes a copy of that noncreature permanent. This causes Metamorphic Alteration to be illegally attached, and it's put into its owner's graveyard. The previously enchanted creature returns to being itself.

The characteristics that will be copied are determined as Metamorphic Alteration's effect first begins to apply. If the copiable values of the chosen creature change later, or if that creature leaves the battlefield, the enchanted creature's characteristics are unaffected.

Metamorphic Alteration copies exactly what is printed on the chosen creature (unless that creature is copying something else or is a token; see below). It doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or any Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, or so on.

You can choose only a creature on the battlefield.