Spirited Escape. Magical Arts Academy, #10

The castle is dark and creepy. It's almost certainly a trap. But the magicians of the academy will risk everything to save one of their own. When the head of the Magical Council betrays the magicians, the Sorcerers have more advantage than they deserve. Isadora and her friends must ride to the rescue, even though they'll have to face their worst fears. It's what the good guys do. Now all they have to do is survive a castle designed to keep everyone who enters.
and never let them go. Spirited Escape is book 10 of Magical Arts Academy, a complete 13 book novella series.