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.
Moody will not attempt to lower a stat that is already at -6 or attempt to increase a stat that is already at +6. Moody will not select the same stat to lower as it raised. If all stats are already at +6, Moody will only decrease one random stat, the same will happen if all stats are already at -6, Moody will only increase one random stat.