Ulamog, the Infinite Gyre — ruling 1

Ulamog's ability triggers as you cast it, and that ability resolves before the spell itself. It resolves even if that spell is countered.

Ulamog, the Infinite Gyre — ruling 2

Lethal damage and effects that say "destroy" won't cause a creature with indestructible to be put into the graveyard. However, a creature with indestructible can be put into the graveyard for a number of reasons. The most likely reasons are if it's sacrificed, if it's legendary and another legendary creature with the same name is controlled by the same player, or if its toughness is 0 or less.

Ulamog, the Infinite Gyre — ruling 3

Annihilator abilities trigger and resolve during the declare attackers step. The defending player chooses and sacrifices the required number of permanents before they declare blockers. Any creatures sacrificed this way won't be able to block.

Ulamog, the Infinite Gyre — ruling 4

If a creature with annihilator is attacking a planeswalker, and the defending player chooses to sacrifice that planeswalker, the attacking creature continues to attack. It may be blocked. If it isn't blocked, it simply won't deal combat damage to anything.

Ulamog, the Infinite Gyre : règles, fonctionnement et interactions (MTG)

Ulamog, the Infinite Gyre 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

When you cast this spell, destroy target permanent. Indestructible Annihilator 4 (Whenever this creature attacks, defending player sacrifices four permanents of their choice.) When Ulamog is put into a graveyard from anywhere, its owner shuffles their graveyard into their library.

Complete guide

Ulamog, the Infinite Gyre is one of the original legendary Eldrazi titans, a massive threat that dominates the battlefield from the moment it is cast. Between its cast trigger, indestructible nature, and devastating Annihilator ability, it stands as one of the most feared creatures in the game.

A Force Upon Casting

Unlike many creatures, Ulamog, the Infinite Gyre has a 'cast trigger.' When you pay the mana to cast this spell, you immediately choose a target permanent to destroy. This ability goes on the stack above Ulamog himself and resolves before he even enters the battlefield. Notably, because this is a triggered ability that happens upon casting, the target is destroyed even if your opponent counters Ulamog with a spell.

Annihilator and Combat

Ulamog features Annihilator 4. This triggers the moment Ulamog is declared as an attacker. The defending player must sacrifice four permanents before they are allowed to declare any blockers. This often clears the way for Ulamog to deal massive damage, as any creatures sacrificed cannot be used to block him later in that phase.

The Infinite Shuffle

Ulamog is difficult to keep in a graveyard. If he is put into a graveyard from anywhere—whether from the battlefield, your hand, or your library—his triggered ability goes on the stack. When it resolves, his owner shuffles their entire graveyard back into their library. This makes Ulamog a potent tool against mill strategies and ensures he can be drawn again later.

Navigating Indestructible

Ulamog is Indestructible, meaning lethal combat damage or 'destroy' effects will not kill him. However, he can still be removed from the battlefield if his toughness becomes 0 or less, if he is exiled, or if his owner is forced to sacrifice him.

Interaction examples

Double the Annihilation

Kozilek, Butcher of Truth

If you attack with both Ulamog, the Infinite Gyre and Kozilek, Butcher of Truth, both Annihilator 4 abilities trigger separately. The defending player must choose and sacrifice a total of eight permanents before they can declare any blockers for either Eldrazi titan.

Dueling Indestructible Giants

Blightsteel Colossus

When Ulamog attacks and is blocked by Blightsteel Colossus, neither creature is destroyed by combat damage because both are Indestructible. However, because Blightsteel Colossus has Infect, it deals damage to Ulamog in the form of -1/-1 counters. If Ulamog receives 11 or more -1/-1 counters, his toughness becomes 0 or less and he is put into the graveyard despite being Indestructible, triggering his shuffle ability.

The Graveyard Shuffle Difference

Blightsteel Colossus

If Ulamog and Blightsteel Colossus are both put into the graveyard from your hand at the same time, their abilities work differently. Blightsteel Colossus has a replacement effect ('instead') that shuffles itself back immediately without using the stack. Ulamog has a triggered ability ('When') that goes on the stack; when it resolves, you shuffle your entire graveyard (including the Colossus if it ended up there, and Ulamog himself) into your library.

Guide written with AI from the official text and rulings. Official English text prevails.

How it works : Ulamog, the Infinite Gyre

Original English text — Wizards of the Coast / Scryfall

#1December 7, 2018· Wizards of the Coast
Ulamog's ability triggers as you cast it, and that ability resolves before the spell itself. It resolves even if that spell is countered.
No other card is named in this ruling.
#2July 1, 2013· Wizards of the Coast
Lethal damage and effects that say "destroy" won't cause a creature with indestructible to be put into the graveyard. However, a creature with indestructible can be put into the graveyard for a number of reasons. The most likely reasons are if it's sacrificed, if it's legendary and another legendary creature with the same name is controlled by the same player, or if its toughness is 0 or less.
No other card is named in this ruling.
#3June 15, 2010· Wizards of the Coast
Annihilator abilities trigger and resolve during the declare attackers step. The defending player chooses and sacrifices the required number of permanents before they declare blockers. Any creatures sacrificed this way won't be able to block.
No other card is named in this ruling.
#4June 15, 2010· Wizards of the Coast
If a creature with annihilator is attacking a planeswalker, and the defending player chooses to sacrifice that planeswalker, the attacking creature continues to attack. It may be blocked. If it isn't blocked, it simply won't deal combat damage to anything.
No other card is named in this ruling.