Activate Phyrexian Altar twice by sacrificing the Wurm tokens, adding ({B} magic symbol) ({B} magic symbol) .
Activate Chainer by paying ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) and 3 life, putting Wurmcoil Engine from your graveyard onto the battlefield.
When Wurmcoil Engine enters the battlefield, Trostani triggers, causing you to gain life equal to Wurmcoil Engine's toughness.