Descent work, this is a story that the player must piece together. I will try to do that down here.

SPOILERS BELOW THIS LINE

There are five endings plus a true ending.

The morse code in the walls reads as follows:
I DONT KNOW HOW LONG ITS BEEN SENSE I MET THAT WOMAN THE WOMAN WHO MADE ME LIKE THIS I DONT KNOW HOW LONG ITS BEEN SENSE FATHR CAST ME AS IDEFB COMING A MONSTER I DONT KNOW HOW LONG I VE BEEN IN THIS BLACK PLACE A PRSON DESIGNED FOR ME BUT IT WILL BE OVER SOON SHE WILL SET ME FREE

Basically, it’s a story that the player must piece together. It goes something like this:

This is the story of the sisters of “Iseult”, “Morgan”, and their abusive father.
Morgan has a curse that turns her into a horrible monster, for that, her father banished her into a pitch black place. Iseult (probably) promised that she would get her out of there and cure her.
(Apparently) a long time passed and Iseult failed to keep her promise. Then, the father were really mad at Iseult (for unknown reasons) and banished her in the pitch black place too.
Morgan was really angry at her sister and started to chase her along the pitch black place.

In almost all the bad endings Morgan kills Iseult. In one ending Iseult kills Morgan, but she becomes the new monster. In the true ending, the sisters make an alliance to kill their father.