"Did you have a nice nap?"
—Liliana Vess

Dread Summons

Each player mills X cards. For each creature card put into a graveyard this way, you create a tapped 2/2 black Zombie creature token. (To mill a card, a player puts the top card of their library into their graveyard.)

Aetherdrift Commander

Each player mills X cards. For each creature card put into a graveyard this way, you create a tapped 2/2 black Zombie creature token.

Foundations

New Capenna Commander

Midnight Hunt Commander

Commander Anthology

Each player puts the top X cards of his or her library into his or her graveyard. For each creature card put into a graveyard this way, you create a tapped 2/2 black Zombie creature token.

If a creature card has an ability that replaces going to the graveyard with moving somewhere else "instead," that card won't count toward the number of Zombies you get. Conversely, creature cards with a triggered ability that removes them from the graveyard when they're put there from anywhere (or your library) will count toward that number.