YA Teen Adventure series, read in 2000. Character drawings and description at beginning of book.

[Jimbo]

A scene had a character sneaking/hiding on pipes and their sweat drips on a guard who tastes the salt and it alerts them. A character wields a staff and the protagonists were in a rebellion a believe. The book was fairly thick sorry I don't have more info it was at the school library and was quite damaged. Thanks.