Shatterskull Minotaur

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.)
Haste

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, exile target nonland permanent an opponent controls until Journey to Oblivion leaves the battlefield.

Synchronized Spellcraft

Synchronized Spellcraft deals 4 damage to target creature and X damage to that creature's controller, where X is the number of creatures in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

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.)

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}

Emeria Captain

Flying, vigilance
When Emeria Captain enters, 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.)

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.)

Shepherd of Heroes

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

Squad Commander

When Squad Commander enters, 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.

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.

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.

Practiced Tactics

Choose target attacking or blocking creature. Practiced Tactics deals damage to that creature equal to twice the number of creatures in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Kabira Outrider

When Kabira Outrider enters, target creature gets +1/+1 until end of turn for each creature in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Ardent Electromancer

When Ardent Electromancer enters, add {R} 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.)

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.)