Indestructible (Effects that say "destroy" don't destroy that permanent. An indestructible creature can't be destroyed by damage.)
As long as your devotion to white (Each in the mana costs of permanents you control counts towards your devotion to white.) and black is less than seven, Athreos isn't a creature.
Whenever another creature you own dies, return it to your hand unless target opponent pays 3 life.