That mod is a reworked version of Unique Isaac Boss Fight created by Laraz, created for Improved & Reworked Foes
Unique to this mod:
- Lazarus and Judas won't fight their postmortem versions (Lazarus II and Dark Judas), but instead they'll fight against a purified version of themselves (*)
- Azazel's sprite has been replaced by Repented Azazel from Salvation (*)
Carried over from predecessor:
- Resprited Angelic Baby while playing as Cain, Lilith, or Jacob (*)
- "Leaving body" mechanic for Lost and Soul
- (*) These changes are now configurable via Mod Config Menu
You can get it here