Mikaeus, the Unhallowed | Rise of the Dark Realms | Ashnod's Altar

(and two other cards)

Rise of the Dark Realms in hand.
All permanents on the battlefield.
Blood Pet does not have a +1/+1 counter on it.
You control another nontoken non-Human creature that does not have a +1/+1 counter on it.

Activate
Blood Pet by sacrificing it, adding ({B} magic symbol) .
When
Blood Pet dies, its undying ability triggers, returning it to the battlefield from your graveyard with a +1/+1 counter on it.
Activate
Blood Pet by sacrificing it, adding ({B} magic symbol) .
Activate
Ashnod's Altar twice by sacrificing
Ardent Elementalist and another nontoken non-Human creature, adding ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) .
When the non-Human creature dies, its undying ability triggers, returning it to the battlefield from your graveyard with a +1/+1 counter on it.
Activate
Ashnod's Altar twice by sacrificing
Mikaeus and the non-Human creature, adding ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) .
Cast
Rise of the Dark Realms by paying ({7} magic symbol) ({B} magic symbol) ({B} magic symbol) , putting all creature cards from all graveyards onto the battlefield under your control.
When
Ardent Elementalist enters the battlefield, it triggers, returning Living Death to your hand from your graveyard.
Repeat.