Cofounder Riverist

Cofounder Riverist, has indestructible &
prowess as long as your team controls a full party.
Whenever a player casts a noncreature spell, you
may have Cofounder Riverist, fight target
creature or planeswalker you don't control.
(Noncreature planeswalkers have a power of 0 when fighting.)
"From our deeds let the first kingless kingdom be born."