Good-Fortune Unicorn

Whenever another creature you control enters, put a +1/+1 counter on that creature.

Chain of Smog

Target player discards two cards. That player may copy this spell and may choose a new target for that copy.

Witherbloom Apprentice

Magecraft — Whenever you cast or copy an instant or sorcery spell, each opponent loses 1 life and you gain 1 life.

Zulaport Cutthroat

Whenever Zulaport Cutthroat or another creature you control dies, each opponent loses 1 life and you gain 1 life.

Ashnod's Altar

Cathars' Crusade

Whenever a creature you control enters, put a +1/+1 counter on each creature you control.

Lethal Vapors

Whenever a creature enters, destroy it.
{0}: Destroy Lethal Vapors. You skip your next turn. Any player may activate this ability.

Grand Abolisher

During your turn, your opponents can't cast spells or activate abilities of artifacts, creatures, or enchantments.

Teferi's Protection

Until your next turn, your life total can't change and you gain protection from everything. All permanents you control phase out. (While they're phased out, they're treated as though they don't exist. They phase in before you untap during your untap step.)
Exile Teferi's Protection.

Corpse Knight

Whenever another creature you control enters, each opponent loses 1 life.

Blood Artist

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.

Ghave, Guru of Spores

Ghave, Guru of Spores enters with five +1/+1 counters on it.
{1}, Remove a +1/+1 counter from a creature you control: Create a 1/1 green Saproling creature token.
{1}, Sacrifice a creature: Put a +1/+1 counter on target creature.