BoI:Afterbirth Devil Room Mechanics

I'm updating my step-for-step breakdown on how your devil door chances are calculated and putting them down here for later reference.

The chance to spawn the door adds up like this:

[*]The BASE chance to spawn the door is 1%.
[*]Have a PENTAGRAM? Add 10%.
[*]Have more than 1 PENTAGRAM? Add another 5%. (If you somehow get the Zodiac item to give you the effects of a Pentagram, that also counts for these 5%)
[*]Have a BLACK CANDLE? Add 15%.
[*]Is your current active item BOOK OF REVELATIONS? +17.5%.
[*]Is your current active item BOOK OF BELIAL? +12.5% (Poor Judas.)
[*]Have you BLOWN UP A BEGGAR on this floor? +35%. (Only normal coin beggars count for this)
[*]Have you suffered RED HEART DAMAGE in this ROOM? If not, +35%.
[*]Have you suffered RED HEART DAMAGE on this FLOOR? If not, +99%.
[*]Have you BLOWN UP A CORPSE (grey dudes in shops, secret rooms etc) on this floor? +10%.


If you've seen a Devil Door before on this run, the following modifiers come on top:
[*]Was the last time you've seen a Devil Door spawn TWO FLOOR BACK? If yes, Chance * 0.5
[*]Was the last time you've seen a Devil Door spawn on the LAST OR THIS FLOOR? If yes, Chance * 0.25


The game now tests whether the check to spawn a Devil Door has [b]failed on this floor[/b] before. If yes, your [b]Chance = 0[/b].
(This makes sure you can't see the door again if it has ever closed, because the check runs every time you step into the boss room)

Now the game checks whether you have [b]Goat Head[/b]. If yes, it increases your chance by +6660%. (4 digit number? Overkill much?)
Since this happens after the aforementioned test, Goat Head can even open up rooms that already closed (or never spawned) before.


Rebirth stopped at this point. However, Afterbirth runs one more check after all this.
Are you playing in GREED MODE? If not, nothing happens and chance calculation ends. If yes:

[*]Is the wave counter < 11? Then your chance is always 0%
[*]Is the wave counter >= 11? Then your chance is always 100%

This will even override Goat Head, so it's totally useless here!