Other Mice you control get +1/+1.
When Mabel, Heir to Cragflame enters, create Cragflame, a legendary colorless Equipment artifact token with "Equipped creature gets +1/+1 and has
vigilance (Attacking doesn't cause this creature to tap.),
trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.), and
haste (This creature can attack, 
and 
as soon as it comes under your control.)" and
equip 
(: Attach to target creature you control. Equip only as a sorcery. This card enters the battlefield unattached and stays on the battlefield if the creature leaves.).
Vintage
