Perplexing Chimera

Whenever an opponent casts a spell, you may exchange control of this creature and that spell. If you do, you may choose new targets for the spell. (If the spell becomes a permanent, you control that permanent.)

Verity Circle

Whenever a creature an opponent controls becomes tapped, if it isn't being declared as an attacker, you may draw a card.
{4}{U}: Tap target creature without flying.

Jinxed Ring

Whenever a nontoken permanent is put into your graveyard from the battlefield, this artifact deals 1 damage to you.
Sacrifice a creature: Target opponent gains control of this artifact. (This effect lasts indefinitely.)

Rewards of Diversity

Whenever an opponent casts a multicolored spell, you gain 4 life.

Kavu Predator

Trample
Whenever an opponent gains life, put that many +1/+1 counters on this creature.

Arasta of the Endless Web

Reach
Whenever an opponent casts an instant or sorcery spell, create a 1/2 green Spider creature token with reach.

Compost

Whenever a black card is put into an opponent's graveyard from anywhere, you may draw a card.

Viridian Revel

Whenever an artifact is put into an opponent's graveyard from the battlefield, you may draw a card.

Jinxed Choker

At the beginning of your end step, target opponent gains control of this artifact and puts a charge counter on it.
At the beginning of your upkeep, this artifact deals damage to you equal to the number of charge counters on it.
{3}: Put a charge counter on this artifact or remove one from it.

Snake Pit

Whenever an opponent casts a blue or black spell, you may create a 1/1 green Snake creature token.

Jinxed Idol

At the beginning of your upkeep, this artifact deals 2 damage to you.
Sacrifice a creature: Target opponent gains control of this artifact.

Illusory Gains

Enchant creature
You control enchanted creature.
Whenever a creature an opponent controls enters, attach this Aura to that creature.

Insight

Whenever an opponent casts a green spell, you draw a card.

Geth's Grimoire

Whenever an opponent discards a card, you may draw a card.

Runic Armasaur

Whenever an opponent activates an ability of a creature or land that isn't a mana ability, you may draw a card.

Rayne, Academy Chancellor

Whenever you or a permanent you control becomes the target of a spell or ability an opponent controls, you may draw a card. You may draw an additional card if Rayne is enchanted.

Cosi's Trickster

Whenever an opponent shuffles their library, you may put a +1/+1 counter on this creature.

Phelddagrif

{G}: Phelddagrif gains trample until end of turn. Target opponent creates a 1/1 green Hippo creature token.
{W}: Phelddagrif gains flying until end of turn. Target opponent gains 2 life.
{U}: Return Phelddagrif to its owner's hand. Target opponent may draw a card.