Bane of the Living — ruling 1

The trigger occurs when you use the Morph ability to turn the card face up, or when an effect turns it face up. It will not trigger on being revealed or on leaving the battlefield.

Bane of the Living — ruling 2

The X in the ability has the same value as the X paid in the Morph ability. This is pretty easy to derive since there is no other source of X.

Bane of the Living : règles, fonctionnement et interactions (MTG)

Bane of the Living 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

Morph (You may cast this card face down as a 2/2 creature for . Turn it face up any time for its morph cost.) When this creature is turned face up, all creatures get -X/-X until end of turn.

How it works : Bane of the Living

Original English text — Wizards of the Coast / Scryfall

#1October 4, 2004· Wizards of the Coast
The trigger occurs when you use the Morph ability to turn the card face up, or when an effect turns it face up. It will not trigger on being revealed or on leaving the battlefield.
Card named in this ruling
Morph
#2October 4, 2004· Wizards of the Coast
The X in the ability has the same value as the X paid in the Morph ability. This is pretty easy to derive since there is no other source of X.
Card named in this ruling
Morph