Just wanted to offer a tip for Monster #44 since he can be a bit of a... nightmare... just so you know this solution does include a bit of a spoiler so be forewarned!
*** Spoiler - click to reveal ***So once you have explored 99% of the map, you can head to O.D.'s room in Livre Ex Machina and he will have a new tome titled the Tome of Conquest. Take out that book, and then fast travel to the Glacial Tomb and proceed west as if you were continuing with the story. You will find O.D. waiting for you, and he will engage you in combat. He's tough! But you have to do it anyways and it's worth it! Once you have defeated him, as a bonus, head back to his library and now you can check out every book at once! Okay, but the real boon here was the shard he gives you. It allows you to freeze every enemy completely still while you have it active. Now, go trigger the bastard demon by sitting on the train seat and waiting for him to appear. There is one trick, you CAN NOT freeze him while he is looking at you or you will continue to take damage. What you want to do is get behind him, and then just hold down that RB button. Now, once he's frozen, you can simply stand there and obliterate him while he stands there helpless. It makes life a lot easier, especially if you have to do him a few times for his shard!