Skyknight Squire

Whenever another creature you control enters, put a +1/+1 counter on this creature.
As long as this creature has three or more +1/+1 counters on it, it has flying and is a Knight in addition to its other types.

Airbender Ascension

When this enchantment enters, airbend up to one target creature.
Whenever a creature you control enters, put a quest counter on this enchantment.
At the beginning of your end step, if this enchantment has four or more quest counters on it, exile up to one target creature you control, then return it to the battlefield under its owner's control.

Mage's Attendant

When this creature enters, create a 1/1 blue Wizard creature token with "{1}, Sacrifice this token: Counter target noncreature spell unless its controller pays {1}."

Wizard

{1}, Sacrifice this creature: Counter target noncreature spell unless its controller pays {1}.

Regal Caracal

Other Cats you control get +1/+1 and have lifelink. (Damage dealt by those creatures also causes you to gain that much life.)
When this creature enters, create two 1/1 white Cat creature tokens with lifelink.

Leonin Vanguard

At the beginning of combat on your turn, if you control three or more creatures, this creature gets +1/+1 until end of turn and you gain 1 life.

Helpful Hunter

Ephemerate

Exile target creature you control, then return it to the battlefield under its owner's control.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Seam Rip

When this enchantment enters, exile target nonland permanent an opponent controls with mana value 2 or less until this enchantment leaves the battlefield.

Basri, Tomorrow's Champion

{W}, {T}, Exert Basri: Create a 1/1 white Cat creature token with lifelink. (An exerted creature won't untap during your next untap step.)
Cycling {2}{W} ({2}{W}, Discard this card: Draw a card.)
When you cycle this card, Cats you control gain hexproof and indestructible until end of turn.

Morningtide's Light

Exile any number of target creatures. At the beginning of the next end step, return those cards to the battlefield tapped under their owners' control.
Until your next turn, prevent all damage that would be dealt to you.
Exile Morningtide's Light.

Arahbo, the First Fang

Other Cats you control get +1/+1.
Whenever Arahbo or another nontoken Cat you control enters, create a 1/1 white Cat creature token.

Plains

Kutzil's Flanker

Flash
When this creature enters, choose one —
• Put a +1/+1 counter on this creature for each creature that left the battlefield under your control this turn.
• You gain 2 life and scry 2.
• Exile target player's graveyard.

Lifelink (Damage dealt by this creature also causes you to gain that much life.)