Dragonskull Summit

Dragonskull Summit enters tapped unless you control a Swamp or a Mountain.
{T}: Add {B} or {R}.

Mountain

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Phyrexian Soulgorger

Cumulative upkeep—Sacrifice a creature. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

Slip Out the Back

Put a +1/+1 counter on target creature. It phases out. (Treat it and anything attached to it as though they don't exist until its controller's next turn.)

Phyrexian Dreadnought

Trample
When Phyrexian Dreadnought enters, sacrifice it unless you sacrifice any number of creatures with total power 12 or greater.

Island

Dark Ritual

Sarkhan's Unsealing

Whenever you cast a creature spell with power 4, 5, or 6, Sarkhan's Unsealing deals 4 damage to any target.
Whenever you cast a creature spell with power 7 or greater, Sarkhan's Unsealing deals 4 damage to each opponent and each creature and planeswalker they control.

Swamp

Maestros Theater

When Maestros Theater enters, sacrifice it. When you do, search your library for a basic Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle and you gain 1 life.

Nyxathid

As Nyxathid enters, choose an opponent.
Nyxathid gets -1/-1 for each card in the chosen player's hand.

Geistwave

Return target nonland permanent to its owner's hand. If you controlled that permanent, draw a card.

Drowned Catacomb

Drowned Catacomb enters tapped unless you control an Island or a Swamp.
{T}: Add {U} or {B}.

Hunted Horror

Trample
When Hunted Horror enters, target opponent creates two 3/3 green Centaur creature tokens with protection from black.