Somberwald Beastmaster dies, triggering Nim Deathmantle, causing you to pay ({4} magic symbol) to return Somberwald Beastmaster from your graveyard to the battlefield, and attach Nim Deathmantle to it.
Somberwald Beastmaster enters the battlefield, creating a 2/2 Wolf, a 3/3 Beast and a 4/4 Beast creature token.
Activate Phyrexian Altar three times by sacrificing the Wolf and two Beasts, adding ({3} magic symbol) .