So I have done all the options with all girls except the "riddle" from the fairy queen.
Whenever I start the endgame quests it ends the same with Evelyn dead and the MC in jail.
Is this the only ending there is?
First, To win the game, you must solve the riddle of the FQ's vision and fulfill the quest she gives you once you've solved it. There are some quests in the game's "todo" list that are optional, but that is not one of them.
Second, during the endgame, when given the choice, you have to go with Evelyn, and you have to have adequate skill at invading minds, or bad things happen to Evelyn. If you have revealed all secrets for all characters who have one, and if you go with Evelyn to confront Thaddeus, you'll be able to save her.
Third, all roads lead to you ending up in jail on the day of coronation. Keep playing, and someone springs you from jail, giving you one last chance to meet with the princess, save the world, and defeat the Big Bad. If you have made the correct choices, you have a chance of surviving your encounter with the Big Bad. If you have not, then you die.