Demonic Rising — ruling 1

If you control zero creatures or more than one creature at the beginning of your end step, the ability won’t trigger. If you control zero creatures or more than one creature when the ability resolves, it will do nothing.

Demonic Rising — ruling 2

Although you must control exactly one creature both when the ability would trigger and when it would resolve in order for the ability to create the Demon token, that creature doesn’t have to be the same one both times. For example, if the ability triggers, then you lose control of your one creature before it resolves, you can cast a creature with flash to make sure you control exactly one creature when the ability resolves.

Demonic Rising : règles, fonctionnement et interactions (MTG)

Demonic Rising 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

At the beginning of your end step, if you control exactly one creature, create a 5/5 black Demon creature token with flying.

How it works : Demonic Rising

Original English text — Wizards of the Coast / Scryfall

#1May 1, 2012· Wizards of the Coast
If you control zero creatures or more than one creature at the beginning of your end step, the ability won’t trigger. If you control zero creatures or more than one creature when the ability resolves, it will do nothing.
No other card is named in this ruling.
#2May 1, 2012· Wizards of the Coast
Although you must control exactly one creature both when the ability would trigger and when it would resolve in order for the ability to create the Demon token, that creature doesn’t have to be the same one both times. For example, if the ability triggers, then you lose control of your one creature before it resolves, you can cast a creature with flash to make sure you control exactly one creature when the ability resolves.
Card named in this ruling
Demon