Mirri the Cursed — ruling 1

If Mirri the Cursed is blocking or blocked by a creature that doesn't have first strike or double strike, Mirri will deal combat damage to that creature, then get a +1/+1 counter, then (if the other creature survived) Mirri will be dealt combat damage.

Mirri the Cursed : règles, fonctionnement et interactions (MTG)

Mirri the Cursed 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

Flying, first strike, haste Whenever Mirri deals combat damage to a creature, put a +1/+1 counter on Mirri.

How it works : Mirri the Cursed

Original English text — Wizards of the Coast / Scryfall

#1March 19, 2021· Wizards of the Coast
If Mirri the Cursed is blocking or blocked by a creature that doesn't have first strike or double strike, Mirri will deal combat damage to that creature, then get a +1/+1 counter, then (if the other creature survived) Mirri will be dealt combat damage.
No other card is named in this ruling.