Strange Cocoon is a trinket in Fiend Folio: RELOADED, a mod for The Binding of Isaac.

Converts all Blue Flies, Blue Spiders, Attack Skuzzes, and Blue Beetles:
• Blue Fly → Blue Spider.
• Blue Spider → Attack Skuzz.
• Attack Skuzz → Blue Beetle.
• Blue Beetle → Blue Fly.

• Check out the trinket description on the mod's external Wiki.
• Download Fiend Folio: RELOADED from the Steam Workshop.