Pestilence Rats

Pestilence Rats's power is equal to the number of other Rats on the battlefield. (For example, as long as there are two other Rats on the battlefield, Pestilence Rats's power and toughness are 2/3.)

Each player loses a third of their life, then discards a third of the cards in their hand, then sacrifices a third of the creatures they control of their choice, then sacrifices a third of the lands they control of their choice. Round up each time.

Seizures

Enchant creature
Whenever enchanted creature becomes tapped, this Aura deals 3 damage to that creature's controller unless that player pays {3}.

Circle of Protection: White

{1}: The next time a white source of your choice would deal damage to you this turn, prevent that damage.

Songs of the Damned

Add {B} for each creature card in your graveyard.

Soul Burn

Spend only black and/or red mana on X.
Soul Burn deals X damage to any target. You gain life equal to the damage dealt, but not more than the amount of {B} spent on X, the player's life total before the damage was dealt, the planeswalker's loyalty before the damage was dealt, or the creature's toughness.

Soul Kiss

Enchant creature
{B}, Pay 1 life: Enchanted creature gets +2/+2 until end of turn. Activate no more than three times each turn.

Spoils of Evil

For each artifact or creature card in target opponent's graveyard, add {C} and you gain 1 life.

Spoils of War

X is the number of artifact and/or creature cards in an opponent's graveyard as you cast this spell.
Distribute X +1/+1 counters among any number of target creatures.

Stench of Evil

Destroy all Plains. For each land destroyed this way, Stench of Evil deals 1 damage to that land's controller unless they pay {2}.

Stromgald Cabal

{T}, Pay 1 life: Counter target white spell.

Touch of Death

Touch of Death deals 1 damage to target player or planeswalker. You gain 1 life.
Draw a card at the beginning of the next turn's upkeep.

Withering Wisps

At the beginning of the end step, if no creatures are on the battlefield, sacrifice this enchantment.
{B}: This enchantment deals 1 damage to each creature and each player. Activate no more times each turn than the number of snow Swamps you control.

Aggression

Enchant non-Wall creature
Enchanted creature has first strike and trample.
At the beginning of the end step of enchanted creature's controller, destroy that creature if it didn't attack this turn.

Cold Snap

Cumulative upkeep {2} (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.)
At the beginning of each player's upkeep, this enchantment deals damage to that player equal to the number of snow lands they control.

Ice Age