I need some ideas, suggestions and feedback about a really crazy and interesting idea one of my players had.
My party was in the Malfeshnekor fight (Book 1, Thistletop, after Nualia's defeat) and one the players, a girl playing and half-elf Druid, realized she couldn't do anything because she ran out of spells and her attacks didn't surpass the RD 10/magic. She then started talking with Malfeshnekor in the middle of the fight, trying to extract some info about the whole dungeon and the strange image of the man talking in Thassilonian a couple of rooms before. Crazy and hungry as he was, he only spoke about "master" Alaznist.
When the party defeated the Greater Barghest (which luckily stabilized with a natural 20), and after a heated discussion with the Cleric of Gorum, the Druid had the idea of letting the creature trapped in the same room and come back later for interrogating him about the past, the Thassilonian Empire (they talked with the Brodert Quink after the Catacombs of Wrath), Alaznist and etc.
The Cleric wanted to kill the outsider right away, but the Druid said the info about the past would be more valuable.
The party was intrigued with the idea and they were all worn-out with all the fighting. They closed the door, took the key and left Malfeshnekor there. The idea of the Druid is to come back later, fully healed and prepared, and try to extract all the info they can before killing the creature.
tl;dr
What do you think about this idea? Is Malfeshnekor willing to tell the party anything or all the years trapped and hungry have more power? If he speaks, what would be recommendable to tell the party without spoiling too much or giving out the name "Karzoug" immediately?