When you unlock this door, search your library for a Room card that doesn't have the same name as a Room you control, reveal it, put it into your hand, then shuffle.
{T}: Add {U}. Cephalid Coliseum deals 1 damage to you. Threshold — {U}, {T}, Sacrifice Cephalid Coliseum: Target player draws three cards, then discards three cards. Activate only if seven or more cards are in your graveyard.
Choose one — • Target opponent discards two cards. • Target opponent reveals their hand. You choose a nonland card from it. That player discards that card.
"Never rely on secondhand description. Always review the memory yourself." —Lazav
First strike, lifelink At the beginning of your second main phase, if you gained life this turn, seek a card with the highest mana value among cards in your library with mana value less than or equal to the amount of life you gained this turn.
I, II — Chainer's Torment deals 2 damage to each opponent and you gain 2 life. III — Create an X/X black Nightmare Horror creature token, where X is half your life total, rounded up. It deals X damage to you.
Discard a card: You may cast a creature spell from your graveyard this turn. Activate only once each turn. Whenever a nontoken creature you control enters, if you didn't cast it from your hand, it gains haste until your next turn.
When Chainsaw enters, it deals 3 damage to up to one target creature. Whenever one or more creatures die, put a rev counter on Chainsaw. Equipped creature gets +X/+0, where X is the number of rev counters on Chainsaw. Equip {3}
Reach When Chainweb Aracnir enters, it deals damage equal to its power to target creature with flying an opponent controls. Escape — {3}{G}{G}, Exile four other cards from your graveyard. Chainweb Aracnir escapes with three +1/+1 counters on it.
Chalice of the Void enters with X charge counters on it. Whenever a player casts a spell with mana value equal to the number of charge counters on Chalice of the Void, counter that spell.
Chamber Sentry enters with a +1/+1 counter on it for each color of mana spent to cast it. {X}, {T}, Remove X +1/+1 counters from Chamber Sentry: It deals X damage to any target. {W}{U}{B}{R}{G}: Return Chamber Sentry from your graveyard to your hand.