Demon of Catastrophes — ruling 1

You must sacrifice exactly one creature to cast Demon of Catastrophes; you can’t cast it without sacrificing a creature, and you can’t sacrifice additional creatures.

Demon of Catastrophes — ruling 2

Players can respond only after Demon of Catastrophes has been cast and all its costs have been paid. No one can try to destroy the creature you sacrificed to prevent you from casting this spell.

Demon of Catastrophes : règles, fonctionnement et interactions (MTG)

Demon of Catastrophes 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

As an additional cost to cast this spell, sacrifice a creature. Flying, trample

How it works : Demon of Catastrophes

Original English text — Wizards of the Coast / Scryfall

#1July 13, 2018· Wizards of the Coast
You must sacrifice exactly one creature to cast Demon of Catastrophes; you can’t cast it without sacrificing a creature, and you can’t sacrifice additional creatures.
No other card is named in this ruling.
#2July 13, 2018· Wizards of the Coast
Players can respond only after Demon of Catastrophes has been cast and all its costs have been paid. No one can try to destroy the creature you sacrificed to prevent you from casting this spell.
No other card is named in this ruling.