the Adventures of Jimmy Crikey: Jade. the Youngest Ever Witch by Wallace Briggs

Jimmy Crikey is the bullied alien born on Earth who became an orphan but chose to stay among his new friends in the magical lands of RoomBelow. His close friend Jade approaches the end of her apprenticeship with Matilda as a witch.There are several challenges to complete before she can graduate as a fully qualified member of the sister’s Coven. Matilda is head of the four guardian witches of Earth’s realms but has been called to move to a higher level. Who will be appointed as her successor?
Jimmy is told not to help Jade directly. She must succeed in the trials using only her skills.
When collapsing roofs threaten the cave world of Lithnia, both Jimmy and Jade’s skills are needed to save Lithnia from the giant, rock-chewing beatles who originated in Egypt as scarabs.
The Sky Islands have been caught in tornado winds and a whirlwind. It is tearing the islands apart. Matilda instructs Jade to go to their aid. Jimmy is forbidden from interfering, but he does help Jade to carry out her plan to save the Islanders. Can the youngest witch overcome the danger?
Madam Coptra, who rules the Sky Islands and has given birth to The Weatherman’s, aka Lord Oron’s, son, Helios, must be introduced to the Coven of sister witches.
The dreaded Giant Scarabs return to their destructive chewing of rocks, threatening the very structure of Roombelow, far away from Lithnia.
Jimmy and Jade trace the beatles resting place to a floating island in the Arctic seas, where the Centaurians, a race from planet Xe in the Alpha Centauri system, are seeking diamonites from Lithnia to protect their planet from gamma rays being emitted by one of their suns. To save their world, they would risk destroying Earth. Jimmy employs XRU, his talkative starship’s navigator, to help the aliens find a material to shield Xe from the deadly rays.
Can Jimmy and Jade save the Centaurian’s world and Earth even as Matilda prepares for her next world of Witchcraft?