Soul Barrier

Whenever an opponent casts a creature spell, Soul Barrier deals 2 damage to that player unless they pay {2}.

Baki's Curse

Baki's Curse deals 2 damage to each creature for each Aura attached to that creature.

Psionic Blast

Psionic Blast deals 4 damage to any target and 2 damage to you.

Exhaustion

Creatures and lands target opponent controls don't untap during their next untap step.

Stinging Licid

{1}{U}, {T}: Stinging Licid loses this ability and becomes an Aura enchantment with enchant creature. Attach it to target creature. You may pay {U} to end this effect.
Whenever enchanted creature becomes tapped, Stinging Licid deals 2 damage to that creature's controller.

Creature Bond

Enchant creature
When enchanted creature dies, Creature Bond deals damage equal to that creature's toughness to the creature's controller.

Island

Mind Bomb

Each player may discard up to three cards. Mind Bomb deals damage to each player equal to 3 minus the number of cards they discarded this way.

Prismatic Lens

{T}: Add {C}.
{1}, {T}: Add one mana of any color.

Zur's Weirding

Players play with their hands revealed.
If a player would draw a card, they reveal it instead. Then any other player may pay 2 life. If a player does, put that card into its owner's graveyard. Otherwise, that player draws a card.

Errant Minion

Enchant creature
At the beginning of the upkeep of enchanted creature's controller, that player may pay any amount of mana. Errant Minion deals 2 damage to that player. Prevent X of that damage, where X is the amount of mana that player paid this way.

Backfire

Enchant creature
Whenever enchanted creature deals damage to you, Backfire deals that much damage to that creature's controller.

Relic Amulet

Whenever you cast an instant, sorcery, or Wizard spell, put a charge counter on Relic Amulet.
{2}, {T}, Remove all charge counters from Relic Amulet: It deals that much damage to target creature.

Quiet Contemplation

Whenever you cast a noncreature spell, you may pay {1}. If you do, tap target creature an opponent controls and it doesn't untap during its controller's next untap step.