Raging Battle Mouse

The second spell you cast each turn costs {1} less to cast.
Celebration — At the beginning of combat on your turn, if two or more nonland permanents entered the battlefield under your control this turn, target creature you control gets +1/+1 until end of turn.

Witchstalker Frenzy

This spell costs {1} less to cast for each creature that attacked this turn.
Witchstalker Frenzy deals 5 damage to target creature.

Lady of Laughter

Flying
Celebration — At the beginning of your end step, if two or more nonland permanents entered the battlefield under your control this turn, draw a card.

Celebrity Fencer

Alliance — Whenever another creature you control enters, put a +1/+1 counter on this creature.

Goddric, Cloaked Reveler

Haste
Celebration — As long as two or more nonland permanents entered the battlefield under your control this turn, Goddric is a Dragon with base power and toughness 4/4, flying, and "{R}: Dragons you control get +1/+0 until end of turn." (It loses all other creature types.)

Ash, Party Crasher

Haste
Celebration — Whenever Ash attacks, if two or more nonland permanents entered the battlefield under your control this turn, put a +1/+1 counter on Ash.

Bespoke Battlegarb

Equipped creature gets +2/+0.
Celebration — At the beginning of combat on your turn, if two or more nonland permanents entered the battlefield under your control this turn, attach this Equipment to up to one target creature you control.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Boss's Chauffeur

This creature enters with a number of +1/+1 counters on it equal to one plus the number of other creatures you control.
Alliance — Whenever another creature you control enters, put a +1/+1 counter on this creature.
When this creature dies, create a 1/1 green and white Citizen creature token for each +1/+1 counter on it.

Chandra, Flamecaller

+1: Create two 3/1 red Elemental creature tokens with haste. Exile them at the beginning of the next end step.
0: Discard all the cards in your hand, then draw that many cards plus one.
−X: Chandra deals X damage to each creature.

Pests of Honor

Celebration — At the beginning of combat on your turn, if two or more nonland permanents entered the battlefield under your control this turn, put a +1/+1 counter on this creature.

Daring Piracy

At the beginning of combat on your turn, create a 1/1 red Pirate creature token with menace and haste. Exile it at the beginning of the next end step.

Battle Screech

Create two 1/1 white Bird creature tokens with flying.
Flashback—Tap three untapped white creatures you control. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Tuinvale Guide

Flying
Celebration — This creature gets +1/+0 and has lifelink as long as two or more nonland permanents entered the battlefield under your control this turn.

Belligerent of the Ball

Celebration — At the beginning of combat on your turn, if two or more nonland permanents entered the battlefield under your control this turn, target creature you control gets +1/+0 and gains menace until end of turn. (It can't be blocked except by two or more creatures.)

Gallant Pie-Wielder

First strike
Celebration — This creature has double strike as long as two or more nonland permanents entered the battlefield under your control this turn.

Leonin Warleader

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

Grand Ball Guest

Celebration — This creature gets +1/+1 and has trample as long as two or more nonland permanents entered the battlefield under your control this turn.

Divine Visitation

If one or more creature tokens would be created under your control, that many 4/4 white Angel creature tokens with flying and vigilance are created instead.