How to unlock Azazel?

[Updated Autopsy Report]

Like, I know I need to make three deals with the devil in one session, but he never appears. Does he appear at random or are there circumstances that must be present?

[Matias]

3 deals with the devil on same run.

[Updated Autopsy Report]

I know, read the description.

[World's best Fox]

yes the devil room appears randomly after the boss. the goat head item increases your chance. you can do a suicide to get Azazel by getting all 3 (if 3 are avaible) at once (presumably killing you or leaving you with 0 hearts) i highly suggest jumping at the chacne to get a devil item whever possible, since Azazel can lead to good runs

[Mr.Joel]

Try beating the boss without taking damage on that floor. That's what usually does it for me.

....Or it could be completely random and I got extremely lucky.

[Matias]

its impossible then, you are doing something wrong, and remeber RUN, not session.

[Zanthar]

To get a devil room try to avoid damage and if you do take damage it lowers the chances pretty low

[K3W3L]

I don't know if these percentages for the Devil Room spawning from the original Isaac also apply to the Rebirth version, but I still think it's worth a read

Base probability = 1%

Add the following percentages:

Have only one Pentagram: +20%
Have multiple Pentagrams: +30%
Have Book of Revelations: +35%
Have Book of Belial: +25%
Killed 1 or more Beggars in current level: +35%
Took no red heart damage from the boss: +35%
Took no red heart damage in current level or Devil/Angel Room appeared the last time Isaac visited the boss room: +99%
Then multiply by one of these:

Devil/Angel Room last spawned in a level 1 less than your current level (or greater; see below): 0.25
Devil/Angel Room last spawned in a level 2 less than your current level: 0.5
The level number the last Devil/Angel Room spawned on is not reset when you start a new run. This means, for example, if you get the Devil Room on Womb 2 in a run and then start a new run, you will continue to be affected by the 0.25 multiplier throughout the whole run until you spawn a new Devil/Angel Room in a sufficiently early level and get 2 or more levels below it (of course at 2 below you will be affected by the 0.5 muliplier instead). Due to this behavior (which is probably a bug), it is recommended to restart the application after every run to maximize your chances of spawning this room.

Source: http://bindingofisaac.wikia.com/wiki/Devil_Room

Basically, the Took no red heart damage confirms what pretty much everyone else said

[ModernMyth]

it's not random. your chance of getting the devil room is increased by not taking red heart damage on the boss

[Swen]

I'm having a problem where I have done this, I made three deals on three different floors. I went on to kill mum's heart but i didn't unlock Azazel

[Leonem]

The Goat Head forces Devil's Room to appear after each bosses.
If you beat a boss and there's no Devil's Room, if you manage to get the Goat Head in the same level, it will force a Devil's Room door to appear in the boss room.

Source : Wikia or Gamepedia, whatever and my own gameplay.

[Doniazade]

Doesn't force devil room on Basement 1 or Cathedral/Sheol though which sort of sucks, need Joker there.

[Kaibun]

It's easy. If there's a room with three deals, just pay them all, even if you end up killing yourself.

[ScarletHaeven]

Originally posted by rpeopler Feelin' Zesty:

Like, I know I need to make three deals with the devil in one session, but he never appears. Does he appear at random or are there circumstances that must be present?

Try The Seed KFKN YMED. At The First Caves You Get An Joker. Use The Joker And You Will Spawn In A Devil Deal Room With 3 Items. Then Just Kill Yourself

[Haloway]

Originally posted by MetalSonicShow:

Originally posted by rpeopler Feelin' Zesty:

Like, I know I need to make three deals with the devil in one session, but he never appears. Does he appear at random or are there circumstances that must be present?

Try The Seed KFKN YMED. At The First Caves You Get An Joker. Use The Joker And You Will Spawn In A Devil Deal Room With 3 Items. Then Just Kill Yourself

You can't use seeds to unlock stuff, Mr. I Capitalize Every Word Because I Failed Primary Level Grammar At School.

[Roarak]

Originally posted by MetalSonicShow:

Originally posted by rpeopler Feelin' Zesty:

Like, I know I need to make three deals with the devil in one session, but he never appears. Does he appear at random or are there circumstances that must be present?

Try The Seed KFKN YMED. At The First Caves You Get An Joker. Use The Joker And You Will Spawn In A Devil Deal Room With 3 Items. Then Just Kill Yourself

This post is almost 2 years old dude...

Edit: One year, sorry I can't count.