The Unbroken Blade

Weapon (greatsword), artifact (requires special attunement, see text)

This legendary weapon has outlasted countless wars, a black hole, and even the god of war that forged it. Whatever its name was at its creation is lost and unknowable, but the blade is as heavy and sharp as ever. The Unbroken Blade is a +4 adamantine greatsword that can be drawn or otherwise readied without an action or move.

The sword’s creator has no worshipers and is long forgotten, but it will bond with a character that survives a singularly destructive event (such as travel through a black hole, a critical hit from a disintegrate spell, or standing on a planet at the moment of its destruction).

Slayer of Gods. When wielded against a god, demigod, legendary demon or similarly powerful foe, or against a creature that has epic boons or blessings, the Unbroken Blade grants advantage on all attack rolls.

Mythic Survivor. The wielder of the Unbroken Blade never suffers additional damage or extra effects from critical hits.

Indestructible. The Unbroken Blade cannot be destroyed short of the application of world-ending force, such as being thrown into a black hole or star.