The critical rate from rings is capped at 32% and rises to 33% after level 200. The quests BSLV UP Special Training, #10 (no. 3410, no. 3411 and no. 3412) raise the ring slot critical rate up to 33%.
Damage amplifiers are items that increase skill damage in the Mission War.
Data from the Cabal Latino server and client (EP33).