Tainted Aether

Whenever a creature enters, its controller sacrifices a creature or land of their choice.

Tribute to the World Tree

Whenever a creature you control enters, draw a card if its power is 3 or greater. Otherwise, put two +1/+1 counters on it.

Indoraptor, the Perfect Hybrid

Bloodthirst X (This creature enters with X +1/+1 counters on it, where X is the damage dealt to your opponents this turn.)
Menace
Enrage — Whenever Indoraptor is dealt damage, choose an opponent at random. Indoraptor deals damage equal to its power to that player unless they sacrifice a nontoken creature of their choice.

Plague Spitter

At the beginning of your upkeep, this creature deals 1 damage to each creature and each player.
When this creature dies, it deals 1 damage to each creature and each player.

Terror of the Peaks

Flying
Spells your opponents cast that target this creature cost an additional 3 life to cast.
Whenever another creature you control enters, this creature deals damage equal to that creature's power to any target.

Florian, Voldaren Scion

First strike
At the beginning of each of your postcombat main phases, look at the top X cards of your library, where X is the total amount of life your opponents lost this turn. Exile one of those cards and put the rest on the bottom of your library in a random order. You may play the exiled card this turn.

Aether Flash

Whenever a creature enters, this enchantment deals 2 damage to it.

Portcullis

Whenever a creature enters, if there are two or more other creatures on the battlefield, exile that creature. Return that card to the battlefield under its owner's control when this artifact leaves the battlefield.

Atarka's Command

Choose two —
• Your opponents can't gain life this turn.
• Atarka's Command deals 3 damage to each opponent.
• You may put a land card from your hand onto the battlefield.
• Creatures you control get +1/+1 and gain reach until end of turn.

Flame Rift

Flame Rift deals 4 damage to each player.

Pyrohemia

At the beginning of the end step, if no creatures are on the battlefield, sacrifice this enchantment.
{R}: This enchantment deals 1 damage to each creature and each player.

Sweltering Suns

Sweltering Suns deals 3 damage to each creature.
Cycling {3} ({3}, Discard this card: Draw a card.)

Marauding Raptor

Creature spells you cast cost {1} less to cast.
Whenever another creature you control enters, this creature deals 2 damage to it. If a Dinosaur is dealt damage this way, this creature gets +2/+0 until end of turn.