Essential

Ondu Rising

Whenever a creature attacks this turn, it gains lifelink until end of turn.
Awaken 4—{4}{W} (If you cast this spell for {4}{W}, also put four +1/+1 counters on target land you control and it becomes a 0/0 Elemental creature with haste. It's still a land.)

Ajani, Nacatl Avenger

+2: Put a +1/+1 counter on each Cat you control.
0: Create a 2/1 white Cat Warrior creature token. When you do, if you control a red permanent other than Ajani, he deals damage equal to the number of creatures you control to any target.
−4: Each opponent chooses an artifact, a creature, an enchantment, and a planeswalker from among the nonland permanents they control, then sacrifices the rest.

Have

Ajani, Nacatl Pariah

When Ajani enters, create a 2/1 white Cat Warrior creature token.
Whenever one or more other Cats you control die, you may exile Ajani, then return him to the battlefield transformed under his owner's control.

Ajani, Nacatl Pariah // Ajani, Nacatl Avenger

Leonin Skyhunter

Ajani's Pridemate

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

Pride Guardian

Defender
Whenever this creature blocks, you gain 3 life.

Revitalize

Cat Soldier

Sunbond

Enchant creature
Enchanted creature has "Whenever you gain life, put that many +1/+1 counters on this creature."

Font of Vigor

{2}{W}, Sacrifice this enchantment: You gain 7 life.

Sword of the Realms

Equipped creature gets +2/+0 and has vigilance.
Whenever equipped creature dies, return it to its owner's hand.
Equip {1}{W}

Halvar, God of Battle

Creatures you control that are enchanted or equipped have double strike.
At the beginning of each combat, you may attach target Aura or Equipment attached to a creature you control to target creature you control.

Halvar, God of Battle // Sword of the Realms

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Festival of Trokin

You gain 2 life for each creature you control.

Ajani's Sunstriker

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

Don't Have

Kemba, Kha Enduring

Whenever Kemba or another Cat you control enters, attach up to one target Equipment you control to that creature.
Equipped creatures you control get +1/+1.
{3}{W}{W}: Create a 2/2 white Cat creature token.

Brave the Elements

Choose a color. White creatures you control gain protection from the chosen color until end of turn.

King of the Pride

Kemba's Skyguard

Flying
When this creature enters, you gain 2 life.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Charmed Stray

Lifelink
When this creature enters, put a +1/+1 counter on each other creature you control named Charmed Stray.

Leonin Warleader

Whenever this creature attacks, create two 1/1 white Cat creature tokens with lifelink that are tapped and attacking.

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.

Gift of Immortality

Enchant creature
When enchanted creature dies, return that card to the battlefield under its owner's control. Return this card to the battlefield attached to that creature at the beginning of the next end step.

Arcbound Mouser

Lifelink
Modular 1 (This creature enters with a +1/+1 counter on it. When it dies, you may put its +1/+1 counters on target artifact creature.)

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.

Brimaz, King of Oreskos

Vigilance
Whenever Brimaz attacks, create a 1/1 white Cat Soldier creature token with vigilance that's attacking.
Whenever Brimaz blocks a creature, create a 1/1 white Cat Soldier creature token with vigilance that's blocking that creature.

Ocelot Pride

First strike, lifelink
Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
At the beginning of your end step, if you gained life this turn, create a 1/1 white Cat creature token. Then if you have the city's blessing, for each token you control that entered this turn, create a token that's a copy of it.

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.

Greatsword of Tyr

Whenever equipped creature attacks, put a +1/+1 counter on it and tap up to one target creature defending player controls.
Equip {W} ({W}: Attach to target creature you control. Equip only as a sorcery.)

Oreskos Sun Guide

Inspired — Whenever this creature becomes untapped, you gain 2 life.

City's Blessing

Plains

Basilisk Collar

Equipped creature has deathtouch and lifelink. (Any amount of damage it deals to a creature is enough to destroy it. Damage dealt by this creature also causes you to gain that much life.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)