Verdant Eidolon by paying ({G} magic symbol) and sacrificing it, adding ({G} magic symbol) ({G} magic symbol) ({G} magic symbol) if you have two or more ({B} magic symbol) available, or ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) otherwise.
Activate
Ashnod's Altar twice by sacrificing
Eternal Witness and another nontoken creature, adding ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) .
Cast
Living Death by paying ({3} magic symbol) ({B} magic symbol) ({B} magic symbol) , causing each player to exile all creature cards in their graveyards, sacrifice all creatures they control, then put all cards exiled this way onto the battlefield.
When
Eternal Witness enters the battlefield, it triggers, returning