Actinium Crawler

Reach, radiate
Exile target creature with flying, {5}{u/b}{u/b}: Mutation 3. (If this creature isn't mutated, put three radiation counters on it and it becomes mutated.)
For as long as Actinium Crawler is mutated and the card exiled with it is a creature card, Actinium Crawler gets +X/+X, where X is the exiled creature's power and gains all of the exiled creature's abilities.