UBOS

UBOS (Fullname "the Ultimate Book Of Spells") is an elderly looking book that has the power to teleport Cassy, Verne and Gus to the centre of the world (and other places they need to be) where they must stop Zarlak.

At some points he tends to be quite grumpy (mostly when Cassy stuffs him in her backpack) and hits the three on the head when he's scolding them. it is revealed throughout the series he is Cassy's great-grandfather. UBOS is also the title character of the series.

Trivia

 * His favourite colour is yellow.