Does the nat 20 still auto hit against adamantine armor? Zoltar 2 years ago See more Does the nat 20 still auto hit against adamantine armor? Yes. — Jeremy Crawford (@JeremyECrawford) June 11, 2018 Share this: Adamantine Armor says “any critical hit against you becomes a normal hit.”, but why does it effect spell crits?Does adamantine armor nullify a natural 20?Does the adamantine armor protect against critical hits inside an antimagic field?