The Bat Medallion is an object that was kept in the Vault until Return of the Kings, where Brady Parker took it and last it retrieving the second Giki-Kiki ruby, and the Tarantula People used it to revive the Mummy. However, Brady, Boomer and Mikayla defeated him and retrieved it.
Mikayla then hid it in a box of the kings' used soap, but Brady and Boomer found it when Boomer moved into Charlotte's building in Sleepless in the Castle and Lanny brought it there, where Boomer put it in the fridge. Charlotte got it, but Mason took it and placed it with Boomer's house warming gifts, so Brady took it to the castle. Mason took it under a tarantula curse, but lost it.
In Meet the Parent, Boz brought it to Rebecca 'Awesome' Dawson's house and hid it in her pillow, but Rebecca later found it, and it dragged her to Kinkow in Long Live the Kings, so Mikayla took it, but Kutamungo took her to the Mummy's temple, where the Tarantula People brought the Mummy back to life. After Boz spat on him by mistake, he transformed into Kaita The Bat-Rider and wore the Bat Medallion in his battles with the kings. It was knocked off somewhere in his fight with Boz and its status is unknown.