Neva, Stalked by Nightmares

Neva, Stalked by Nightmares (1UB) is a legendary 2/3 Human Noble with "Whenever Neva, Stalked by Nightmares deals combat damage to a player, each player mills three cards" and "Whenever a creature card is put into an opponent's graveyard from anywhere, exile it and you create a 1/1 black Nightmare creature token with menace." Excellent commander for Dimir mill strategies generating tokens while disrupting graveyard plans.