Soul Warden

Whenever another creature enters, you gain 1 life.

Bonesplitter

Benevolent Bodyguard

Sacrifice this creature: Target creature you control gains protection from the color of your choice until end of turn.

Celestial Unicorn

Whenever you gain life, put a +1/+1 counter on this creature.

Answered Prayers

Whenever a creature you control enters, you gain 1 life. If this enchantment isn't a creature, it becomes a 3/3 Angel creature with flying in addition to its other types until end of turn.

Quicksand

{T}: Add {C}.
{T}, Sacrifice this land: Target attacking creature without flying gets -1/-2 until end of turn.

Thraben Inspector

When this creature enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Kor Skyfisher

Flying
When this creature enters, return a permanent you control to its owner's hand.

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Squadron Hawk

Flying
When this creature enters, you may search your library for up to three cards named Squadron Hawk, reveal them, put them into your hand, then shuffle.

Journey to Nowhere

When this enchantment enters, exile target creature.
When this enchantment leaves the battlefield, return the exiled card to the battlefield under its owner's control.

Plains

Luminous Phantom

Flying
Whenever another creature you control leaves the battlefield, you gain 1 life.
If Luminous Phantom would be put into a graveyard from anywhere, exile it instead.

Lunarch Veteran

Whenever another creature you control enters, you gain 1 life.
Disturb {1}{W} (You may cast this card from your graveyard transformed for its disturb cost.)