Fisrt I write down: "But I have kill a single enemie that drops a key, I have that key ... but can't in any library"
Sorry, I wasn't completly: there're 2 enemies adn both enemies left a key when they die! One key for a chest an one for the door of teh library
I look over that one key of the library

lol
I have found also the name of that Laiken's Demon

Thanks for help
