As long as your opponents control no creatures, Erebos's Titan has indestructible. (Damage and effects that say "destroy" don't destroy it.)
Whenever a creature card leaves an opponent's graveyard, you may discard a card. If you do, return Erebos's Titan from your graveyard to your hand.
6/22/2015 Damage dealt to a creature with indestructible remains marked on that creature. If Erebos’s Titan has lethal damage marked on it and it loses indestructible (perhaps because your opponent controlled no creatures and then gained control of one), Erebos’s Titan will be destroyed.
6/22/2015 The last ability triggers only if Erebos’s Titan is in your graveyard.
6/22/2015 In a multiplayer game, the last ability won’t trigger when a player with a creature card in their graveyard leaves the game.