Mirri, Weatherlight Duelist

Oracle Text

First strike

Whenever Mirri, Weatherlight Duelist attacks, each opponent can't block with more than one creature this combat.

As long as Mirri, Weatherlight Duelist is tapped, no more than one creature can attack you each combat.

Card Rulings

8/25/2017 While Mirri is tapped, there’s no restriction on how many creatures can attack planeswalkers you control.
8/25/2017 Tapping Mirri after creatures have attacked will not remove creatures from combat.