"This will work," Gerrard called to the elves as he used the forge to strengthen the aboroth, "but if it doesn't, we won't survive to care."

Thran Forge

{2}: Until end of turn, target nonartifact creature gets +1/+0 and becomes an artifact in addition to its other types.

The List

Weatherlight

o2: Until end of turn, target nonartifact creature gets +1/+0 and is an artifact creature.

Now becomes an artifact in addition to its other types.

If Thran Forge’s ability is activated targeting a nonartifact creature, then it’s activated again in response targeting the same creature, the second instance will resolve. The first instance will then be countered for having an illegal target, since the target is no longer a nonartifact creature.