Love me some good old chatroom horror. This was actually a great chatroom game where everyone seemed really human and seemed like actual friends! That made the game that much more relatable and invest able in the characters. (Video below if anyone wants to watch!)
The way the text was 'taken over' by the entity was great and well done, and honestly an overall great game.
The only things I would suggest (If you will update the game in the future/ make another game similar to this.) would be to add more choices, that would make the players invest more in the story and give a good contrast to the non controllable choices. And one other thing is to give the entity an actual reason to do what it is doing other than 'a need to complete its task.' For example, adding a list of rules for summoning the entity and also making the players part of summoning the entity rather than one of the friends summon them would make it feel more personal and adding a list of rules where you can add 'entity will reveal everyone's secrets until there is nothing left' or something like that will give the baddie in the game proper backing to be actual evil (And also maybe a different reason for the entity to harm others than just cheating on people, I personally felt like just cheating on members wasn't very impact enough to justify the deaths of either one of the choices of people. Though not condoning cheating in any way.)
But yeah, it was a great game with a great atmosphere as it takes time to build up to things and was really surprised when the links went to actual things; it added a lot of depth to the story and game that not many other games have! (Though I think the first link didn't work for me no matter how many times I clicked on it.) The personal messaging was also well done, as it added another depth to the game and made things that much more suspenseful.
Congrats on a great game and good luck for future games!