Judas is one of the more interesting characters in The Binding of Isaac: Rebirth. He has a stronger start than Isaac thanks to his higher damage and Book of Belial, but he starts with only one heart, which makes him a risky choice. If you want to unlock him, here’s what you need to do.
The Binding of Isaac Rebirth How to Unlock Judas
To unlock Judas, you must defeat Satan (Satan) in Sheol. Sound simple? Maybe so, but if you’re just starting the game, it can be quite a challenge. Here’s how best to approach this task.
How to get to Sheol The Binding of Isaac: Rebirth
Defeat Mom’s Heart several times – then you will unlock alternative paths, including Sheol.

Use the Devil Pact (Devil Deal) if the option to go to Sheol appears after fighting It Lives (an upgraded version of Mom’s Heart).

Use the Black Roses (Black Rune) or the Devil Room Entrance (Devil Room) if it opens after fighting the main boss.

How to defeat Satan The Binding of Isaac Rebirth
Satan consists of three phases:
The Fallen – you fight two flying demons that shoot lasers.
Satan – a huge head that shoots projectiles and summons devils.
Satan’s gigantic legs – watch out for attacks from above!
Some tips:
Collect strong items – Tears Up, Damage Up and good active items (such as The Book of Belial or The Nail) will make the fight easier.
Watch out for blows – remember that you will unlock Judas only after defeating Satan for the first time, so don’t risk too much.
If you have a problem, play with Azazel – his innate laser (Brimstone) will dispel bosses quickly.
CONCLUSION
Judas is a great character in The Binding of Isaac: Rebirth, but it requires a bit of effort to get him. The key to success is getting to Sheol and successfully fighting Satan. Good luck and may the RNG be with you.