Ardent Electromancer

When Ardent Electromancer enters the battlefield, add {R} for each creature in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Ash, Party Crasher

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

Multiclass Baldric

Equipped creature has lifelink if you control a Cleric, deathtouch if you control a Rogue, haste if you control a Warrior, and flying if you control a Wizard.
As long as you have a full party, prevent all damage that would be dealt to equipped creature.
Equip {2}

Thundering Sparkmage

When Thundering Sparkmage enters the battlefield, it deals X damage to target creature or planeswalker, where X is the number of creatures in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Emeria Captain

Flying, vigilance
When Emeria Captain enters the battlefield, put a +1/+1 counter on it for each creature in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Allied Assault

Up to two target creatures each get +X/+X until end of turn, where X is the number of creatures in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Sol Ring

Farewell

Choose one or more —
• Exile all artifacts.
• Exile all creatures.
• Exile all enchantments.
• Exile all graveyards.

Pinkie Pie

Whenever you cast a spell with a smile in its art, create a tapped Treasure token.
Everypony's Invited — Your party consists of each creature you control, and your party is always full.

Archpriest of Iona

Archpriest of Iona's power is equal to the number of creatures in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)
At the beginning of combat on your turn, if you have a full party, target creature gets +1/+1 and gains flying until end of turn.

Sea Gate Colossus

This spell costs {1} less to cast for each creature in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Journey to Oblivion

This spell costs {1} less to cast for each creature in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)
When Journey to Oblivion enters the battlefield, exile target nonland permanent an opponent controls until Journey to Oblivion leaves the battlefield.

Shepherd of Heroes

Flying
When Shepherd of Heroes enters the battlefield, you gain 2 life for each creature in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Grotag Bug-Catcher

Trample
Whenever Grotag Bug-Catcher attacks, it gets +1/+0 until end of turn for each creature in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Amulet of Vigor

Whenever a permanent enters the battlefield tapped and under your control, untap it.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Squad Commander

When Squad Commander enters the battlefield, create a 1/1 white Kor Warrior creature token for each creature in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)
At the beginning of combat on your turn, if you have a full party, creatures you control get +1/+0 and gain indestructible until end of turn.

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.

Stick Together

Each player chooses a party from among creatures they control, then sacrifices the rest. (To choose a party, choose up to one each of Cleric, Rogue, Warrior, and Wizard.)