Ok
So after completing game 4-5 times I can tell you.
First ending, after running from black beast just into next room, go back into same room where black beast was, don't worry he is gone. Go all the way up and enter next room, there will be save statue and beside it there will be a door on the right, enter and go all the way up. Congrats, you got first ending
Second ending, before beating last boss you have to get basement key to tainted chapel which you can get from snake man in swamp beside elevator, there you will fing sword of vow, after that kill last boss and interact with his body, voilà.
Third ending, kill last boss, there will be fire, interact with it and you'll find elevator wich leads to same room from first ending, again go into right door and all the way up, third one complete.
Fourth, hardest one. After running away from flying red thing in conjuring world Lir, there will be hole in wall, enter it, there will be a small corridor to the right enter it and you will be transported to outdoors location, at end of it there will be Esbets Soul, take it, its crucial because if you won't take it now you can't come to this location again which locks you out of this ending.
Next, play game normally, until you get to catacombs where you have to put 4 Blood of Sovereign on pedestals, beside there will be Save statue and Idol, enter it but immediately go to the left until you find an breakable wall, break it, enter and ascend Esbets soul on pedestal . This one is crucial to do because if you kill boss of this area you can't get it. Next, on swamp there will be same pedestal, beat the boss, use pedestal, all good. Last one, in last location there will be boss, huge "Tower Knight", after killing him, behind him there will be illusory wall, enter, search for pedestal, ascend your soul and of course beat last boss. Congratulations! You have True Ending.
There is Fifth ending, with Valka sword, but I could trigger it, so i can't help with this one.
Good luck!