Elfira, the Watcher

Indestructible, Trample, Menace, Vigilance
Elfira, the Watcher gets +1/+1 for each
other Elf you control.
As long as you control seven or more other Elves,
they gain Indestructible, Trample, Menace, and Vigilance.
{t}: Add one mana of any color. Spend this mana
only to cast an Elf creature spell.