Activate Viscera Seer 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 Maskwood Nexus, Bishop of Wings' first ability triggers, causing you to gain 4 life.
Resolve the Viscera Seer ability.
Repeat.
With Maskwood Nexus quietly reshaping the battlefield by granting every creature type to your creatures and tokens, your 1/1 Spirit tokens are born as Angels to fuel this sacred engine. When you sacrifice a token to Viscera Seer to scry through your library, its death immediately triggers Bishop of Wings to create a fresh 1/1 Spirit token in its place. Because that new token enters as an Angel thanks to the Nexus, Bishop of Wings triggers again to grant you 4 life, allowing you to loop this infinite sacrifice, death, and lifegain cycle indefinitely.