Allied Assault — ruling 1

The value of X is determined only as Allied Assault resolves. Once that happens, the value of X won’t change later in the turn even if the number of creatures in your party changes.

Allied Assault — ruling 2

To determine “the number of creatures in your party,” check whether you control a Cleric, whether you control a Rogue, whether you control a Warrior, and whether you control a Wizard. The number is the total number of those checks to which you answered yes. Each creature you control can be counted for only one of those checks.

Allied Assault — ruling 3

If a creature has more than one party creature type, and there are multiple ways to count that creature that could result in a different number of creatures in your party, the highest such number is used. For example, if you control a Cleric and a Cleric Wizard, the number of creatures in your party is two. You can’t choose to have it be just one by counting the Cleric Wizard first as a Cleric.

Allied Assault — ruling 4

An ability referring to the number of creatures in your party gets a number from zero to four. Such abilities never ask which creatures are in your party, and you never have to designate specific creatures as being in your party. You can’t choose to exclude creatures from this count to lower the number.

Allied Assault : règles, fonctionnement et interactions (MTG)

Allied Assault is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

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.)

How it works : Allied Assault

Original English text — Wizards of the Coast / Scryfall

#1September 25, 2020· Wizards of the Coast
The value of X is determined only as Allied Assault resolves. Once that happens, the value of X won’t change later in the turn even if the number of creatures in your party changes.
No other card is named in this ruling.
#2September 25, 2020· Wizards of the Coast
To determine “the number of creatures in your party,” check whether you control a Cleric, whether you control a Rogue, whether you control a Warrior, and whether you control a Wizard. The number is the total number of those checks to which you answered yes. Each creature you control can be counted for only one of those checks.
No other card is named in this ruling.
#3September 25, 2020· Wizards of the Coast
If a creature has more than one party creature type, and there are multiple ways to count that creature that could result in a different number of creatures in your party, the highest such number is used. For example, if you control a Cleric and a Cleric Wizard, the number of creatures in your party is two. You can’t choose to have it be just one by counting the Cleric Wizard first as a Cleric.
No other card is named in this ruling.
#4September 25, 2020· Wizards of the Coast
An ability referring to the number of creatures in your party gets a number from zero to four. Such abilities never ask which creatures are in your party, and you never have to designate specific creatures as being in your party. You can’t choose to exclude creatures from this count to lower the number.
No other card is named in this ruling.