Moonshaker Cavalry — ruling 1

The value of X is determined only as Moonshaker Cavalry's triggered ability resolves, potentially including Moonshaker Cavalry itself. It won't change later in the turn if the number of creatures you control changes.

Moonshaker Cavalry — ruling 2

Moonshaker Cavalry's triggered ability affects only creatures you control at the time it resolves. Creatures you begin to control later in the turn won't be affected.

Moonshaker Cavalry : règles, fonctionnement et interactions (MTG)

Moonshaker Cavalry 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

Flying When this creature enters, creatures you control gain flying and get +X/+X until end of turn, where X is the number of creatures you control.

How it works : Moonshaker Cavalry

Original English text — Wizards of the Coast / Scryfall

#1September 1, 2023· Wizards of the Coast
The value of X is determined only as Moonshaker Cavalry's triggered ability resolves, potentially including Moonshaker Cavalry itself. It won't change later in the turn if the number of creatures you control changes.
No other card is named in this ruling.
#2September 1, 2023· Wizards of the Coast
Moonshaker Cavalry's triggered ability affects only creatures you control at the time it resolves. Creatures you begin to control later in the turn won't be affected.
No other card is named in this ruling.