We have begun migration of most wikis to our new host, Amazon Web Services. All but the top 100 wikis are in read-only mode until the migration is complete. Estimated completion: TBD -- Update: Fri 10/20 11pm UTC - We have encountered some unexpected issues. Our staff is working around the clock to complete this process as quickly as possible. Thank you for your patience.
From Terraria Wiki
The Broken Bat Wing is a rare Hardmode crafting material used solely to craft Bat Wings. It has a 1/40 (2.5%) chance of being dropped by Vampires during a Solar Eclipse.