Dûm, the Seventh Mountain

Flying, Vigilance.
Whenever Dum, the Seventh Mountain
becomes an artifact creature, creatures you
control get +X/+X until end of turn, where
X is the number of Dwarf creatures you control.
Crew 5 (Tap any number of creatures you control
with total power 5 or more: This Vehicle becomes an
artifact creature until end of turn.)