@IAmTheImagineerThe DMG for D&D 5e Monster statistics chart does not go beyond AC 19, how would I then calculate an AC of 20+ for a creature? Heh. For 5e rules, @JeremyECrawford is your man. THE expert. (When I'm DMing, I don't bother w/math; it's the PCs' story.)

— Ed Greenwood (@TheEdVerse) October 31, 2016