Merfolk Thaumaturgist

{T}: Switch target creature's power and toughness until end of turn.

Miscast

Counter target instant or sorcery spell unless its controller pays {3}.

Sorceress Queen

{T}: Target creature other than Sorceress Queen has base power and toughness 0/2 until end of turn.

Swamp

Mental Misstep

({U/P} can be paid with either {U} or 2 life.)
Counter target spell with mana value 1.

Mire in Misery

Each opponent sacrifices a creature or enchantment of their choice.

Exsanguinate

Each opponent loses X life. You gain life equal to the life lost this way.

Island

Stifle

Counter target activated or triggered ability. (Mana abilities can't be targeted.)

Go for the Throat

Mana Leak

Counter target spell unless its controller pays {3}.

Torment of Hailfire

Repeat the following process X times. Each opponent loses 3 life unless that player sacrifices a nonland permanent of their choice or discards a card.

Hunted Horror

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

Dark Ritual

Grim Wanderer

Flash
Tragic Backstory — Cast this spell only if a creature died this turn.

Phyrexian Dreadnought

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

Daze

You may return an Island you control to its owner's hand rather than pay this spell's mana cost.
Counter target spell unless its controller pays {1}.

Murkwater Pathway

Clearwater Pathway

Clearwater Pathway // Murkwater Pathway

Force of Despair

If it's not your turn, you may exile a black card from your hand rather than pay this spell's mana cost.
Destroy all creatures that entered this turn.