Cast Ghouls' Night Out by paying ({3} magic symbol) ({B} magic symbol) ({B} magic symbol) , returning Shipwreck Dowser from your graveyard to the battlefield, and at least two other creatures from your opponents' graveyards to the battlefield under your control.
When Shipwreck Dowser and the creatures enter the battlefield, Blessed Sanctuary triggers once for each creature, and Shipwreck Dowser triggers once.
Resolve the Shipwreck Dowser trigger, returning Ghouls' Night Out from your graveyard to your hand.
Resolve all Blessed Sanctuary triggers, creating that many 2/2 Unicorn creature tokens.
Activate Phyrexian Altar five times by sacrificing Shipwreck Dowser, two creatures your opponents own, and two Unicorns, adding ({3} magic symbol) ({B} magic symbol) ({B} magic symbol) .