Talk:THAC0/@comment-44643388-20191211095426/@comment-3045005-20191211125458

That is a good question. I don't have the answer to it here, I can say that in the pencil-and-paper rules for most editions of D&D, only a natural 20 is an auto-hit. Expanded crit range means if that roll of e.g. 19 would still hit, then it's a crit, but it's not automatic. I don't believe this situation comes up often, usually a roll of 19 plus bonuses is going to hit appropriately-leveled enemies, but it can happen.