Arcane Crest is a job ability from Final Fantasy XI. It can be obtained by Dark Knights at level 87. It has a duration of 3 minutes and a recast time of 10 minutes. The ability lowers accuracy, evasion, magic accuracy, magic evasion, and TP gain for arcana. It can only be used if the target belongs to the arcana group of enemies.
Arcane is a synonym for esoteric. It refers to various secret philosophical and religious doctrines and traditions.