
When Acererak enters, if you haven't completed Tomb of Annihilation, return Acererak to its owner's hand and venture into the dungeonventure into the dungeonEnter the first room or advance to the next room..
Whenever Acererak attacks, for each opponent, you create a 2/2 black Zombie creature token unless that player sacrifices a creature of their choice.
Hover an underlined rule to see what it means.
Read from the rules text. A card that enables a keyword makes or is the thing; a card that rewards it gets better when you have it. Two cards interact when one enables what the other rewards.
This card refers to dungeons. These are the dungeon cards you can venture into; taking the initiative always uses Undercity. Dungeons sit outside your deck, so you don't need to add them to it.