Tips for key pieces?

[Tea]

im trying to kill mega satan with judas but i don't get angel rooms

[Desticler]

1) DO NOT get any items that cost heart containers (From Devil Deals and Black Market). This causes angel rooms to have 0% chance of appearing.
2) Once you get 1 key piece, the chance of getting next angel room becomes mush higher.
3) By hitting spikes in Sacrifice Room, you can become blessed. Once you see the message, chance of getting angel room is, I think, 100%, even if you failed to follow point 1.
4) Hitting spikes in Sacrifice Room a LOT OF times causes angel bosses to spawn, and they drop key pieces.

[BOYCOTT]

you can consider taking goat head item though in case you get duality later to get key pieces that way, it doesn't seem to be too uncommon.

[Fracastador]

Originally posted by Too-DAMN-Much:

you can consider taking goat head item though in case you get duality later to get key pieces that way, it doesn't seem to be too uncommon.

I personally have only ever seen duality about 5 times, so I don't recommend buying a goat head from a devil deal in hopes of getting duality later.
If you can manage get enough health, using the sacrifice rooms is the most consistant way.
There are also super secret rooms that sometimes have angel statues in them and trigger the boss fights when blown up. You can get key pieces from these.
I've read that each key piece will only spawn once per run, so don't forget to pick any up that you won from a boss, and don't reroll them for angel items.

Weirdest, probably least helpful tip is that if you generate a boss in an angel room with the delirious item and kill it, it will drop a key piece if you haven't already spawned both pieces.

[The Renderer]

You can also bomb angels in secret rooms to get a key piece (provided you already got the "The Angels Await" unlock).

And you can use Dad's Key to unlock the Mega Satan room instead of getting key pieces from angels.