From Bulbapedia, the community-driven Pokémon encyclopedia.
AMU was a semi-popular Pokémon Trading Card Game deck archetype in late 2008. AMU stands for Azelf, Mesprit, and Uxie: the three key Pokémon in this deck. The deck's strategy centered around getting Mesprit LV.X, Uxie LV.X, and Azelf LV.X in play as fast as possible and consistently doing 200 damage with Mesprit LV.X's Supreme Blast attack. The deck faced severe consistency problems and, although it saw a small competitive play revival with the release of Level Max in the Platinum expansion, AMU was a short-lived and fairly unpopular archetype.