Activate Shilgengar by sacrificing another creature.
When the creature dies, Bishop of Wings' second ability triggers, creating a 1/1 Spirit creature token.
When the Spirit token enters the battlefield as an Angel due to Arcane Adaptation, Bishop of Wings' first ability triggers, causing you to gain 4 life.
Resolve the Shilgengar ability.
Repeat.
This clever loop turns Shilgengar, Sire of Famine into a relentless sacrifice engine by leaning on Arcane Adaptation to rewrite creature types across the board. Because Arcane Adaptation turns every creature you own—including the 1/1 white Spirit creature tokens created by Bishop of Wings—into Angels, sacrificing a creature to Shilgengar triggers the Bishop to churn out replacement tokens that instantly enter as Angels and pad your life total by 4 thanks to its first ability. Shilgengar happily converts those sacrificed bodies into Blood tokens, fueling an endless cascade of enters-the-battlefield, leaves-the-battlefield, and death triggers while keeping your life total safely in the stratosphere.