Creating an animated mask from a alpha clip

You could try the image tracing function, but to be honest, using a mask on such a detailed artwork probably doesn't make a lot of sense. The trace function would eventually simply crash becasue there are limits how many masks AE can handle and nhow many points those masks can have, in fact meaning that it may not even be able to correctly trace the whole perimeter and cut out prematurely. Therefore the better question probably is what you actualyl want to do and what you would need the mask for. there may be better techniques without masks or shape layers...

Mylenium