Ephara's Mount

Indestructible
Collaborate - At the beginning of each upkeep, if
you control a creature that doesn't share a color
with this creature, exile Ephara's Mount, then
return it to the battlefield, except it is an Aura
enchantment with enchant creature. It becomes
a creature again if it's not attached to a creature.
Enchanted creature gets +2/+2 and has indestructible.