Underworld6 books in series
Level Up or Die! Publisher's Summary
Elorion has just finished a VR gaming session to find a monster waiting for him. With 19 other students who have also been kidnapped, he is now subject to the whims of a thousand year old succubus, and he must survive deep under the Earth in the lost realm of the Underworld.
Gifted with the ability to use magic and advance in power, he is given an ultimatum: Level up or die!