Whenever one or more creatures a player controls deal combat damage to you, that player takes the initiative.
Whenever you take the initiative and at the beginning of your upkeep, venture into Undercity. (If you're in a dungeon, advance to the next room. If you're not, enter Undercity. you can take the initiative even if you already have it.)
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Undercity
Secret Entrance:
Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
Forge:
Put two +1/+1 counters on target creature.
Lost Well:
Scry 2.
Trap!:
Target player loses 5 life.
Arena:
Goad target creature.
Stash:
Create a Treasure token.
Archives
Draw a card.
Catacombs:
Create a 4/1 black Skeleton creature token with menace.
Throne of the Dead Three:
Reveal the top ten cards of your library. Put a creature card from among them onto the battlefield with three +1/+1 counters on it. It gains hexproof until your next turn.
