AustLit

"The King of Nuevah is dead, murdered by his own brother. Evil forces threaten to plunge Nuevah into Darkness...unless a lost prince - ambushed and sold into slavery years before - returns to claim his rightful throne.
Four Vahian soldiers embark on an epic journey in search of the lost prince. They are joined by a young bondservant called Teal, whose instinctive skill with weapons reveals the mystery of his birthright. Teal finds a ring in the subterranean city of Perdu which gives him mystic powers and enables him to draw together others with identical rings and similar abilities. Under Teal's guidence, the seven Usare must use the combined might of the rings to form a Circle of Light against the forces of darkness who threaten to engulf all the lands in war.
Teal's perilous odyssey leads the Usare across many strange lands and sets them against horrifying creatures, savage foes and age-old magic. As they venture closer to the Dark Forces, Teal learns of a terrifying ancient prophecy . . .that he alone must fulfill." 

Source: bookseller's website (https://www.qbd.com.au/chronicles-of-the-custodians-1-circle-of-light/martin-middleton/9780330271509/