Alien Angel 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

First strike, vigilance Whenever an opponent casts a creature spell, this permanent isn't a creature until end of turn.

How it works : Alien Angel

Original English text — Wizards of the Coast / Scryfall

No additional ruling has been published for this card.

Interactions with other cards

These cards' text mentions Alien Angel.

Blink

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after IV.) I, III — Choose target creature. Its owner shuffles it into their library, then investigates. (They create a Clue token.) II, IV — Create a 2/2 black Alien Angel artifact creature token with first strike, vigilance, and "Whenever an opponent casts a creature spell, this token isn't a creature until end of turn."