Strange Times. The Multiversal Chronicles, #6

Disaster in the Multiverse! Merlin and his alien friends at the Multiversal Research Centre are under attack. Kitty Strange and her team are the only people who can save them. But what can they do? Jumping blind and ending up on Avalonia, they're met by a group of young elves who were expecting them. As they start to learn about the mysterious Morwen and the large elf army she's building, they're interrupted by recruiters and who want to enlist them in the army.
Split into two groups, they find themselves in worse trouble. So begins a scary adventure that takes them to the island of Avalon and Morwen herself. Are they supposed to help her or beat her? And how will all this save Merlin and his friends?