Eidolon of Countless Battles  (3) 
Enchantment Creature — Spirit (0/0) 
Bestow  (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Eidolon of Countless Battles and enchanted creature each get +1/+1 for each creature you control and +1/+1 for each Aura you control.