Phantom Centaur — ruling 1

If this creature would be dealt damage from multiple sources at the same time (say, because it's blocked by multiple creatures), all of the damage is prevented and only one +1/+1 counter is removed.

Phantom Centaur — ruling 2

If damage that would be dealt to this creature can't be prevented, the damage is dealt and a +1/+1 counter is removed from this creature.

Phantom Centaur — ruling 3

If this creature has no +1/+1 counters on it (but is still on the battlefield because something else is raising its toughness), damage that would be dealt to it is still prevented.

Phantom Centaur — ruling 4

If this card is going to take damage from a black source, you can choose to apply Protection from Black's damage prevention ability prior to applying this card's built-in ability. This means you don't have to remove a counter.

Phantom Centaur : règles, fonctionnement et interactions (MTG)

Phantom Centaur 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

Protection from black This creature enters with three +1/+1 counters on it. If damage would be dealt to this creature, prevent that damage. Remove a +1/+1 counter from this creature.

How it works : Phantom Centaur

Original English text — Wizards of the Coast / Scryfall

#1December 8, 2022· Wizards of the Coast
If this creature would be dealt damage from multiple sources at the same time (say, because it's blocked by multiple creatures), all of the damage is prevented and only one +1/+1 counter is removed.
No other card is named in this ruling.
#2December 8, 2022· Wizards of the Coast
If damage that would be dealt to this creature can't be prevented, the damage is dealt and a +1/+1 counter is removed from this creature.
No other card is named in this ruling.
#3December 8, 2022· Wizards of the Coast
If this creature has no +1/+1 counters on it (but is still on the battlefield because something else is raising its toughness), damage that would be dealt to it is still prevented.
No other card is named in this ruling.
#4October 4, 2004· Wizards of the Coast
If this card is going to take damage from a black source, you can choose to apply Protection from Black's damage prevention ability prior to applying this card's built-in ability. This means you don't have to remove a counter.
No other card is named in this ruling.