F.E.V. Infected: Deathclaw

You've been exposed to the F.E.V., or Forced Evolution Virus, and perhaps even nuclear radiation. The resulting genetic cocktail has modified your genome giving you the ability to turn into the ultimate killing machine: a Deathclaw. Once per long rest, instead of falling to 0 HP from an attack you instead transform violently, because the mindless murder machine you likely are anyway, you will remain in a Deathclaw form for up to 10 round (1 minute) or until you once again reach 0 hp, upon transforming back from reaching 0 hp you will fall into death save and gain 2 levels of exhaustion. Upon transforming back from time you will be on 1 hp and gain 1 level of exhaustion.