>At the end of each turn, Moody raises one of the stats of the Pokémon with this Ability by two stages (at random), then decreases another stat by one stage (at random). It can select accuracy and evasion.
--Bulbapedia
This is the reason it is banned in the Meta-game. It is waaay too random and hax-y to be determined, and therefore often screws up games.
