**SPOILERSPOILERSPOILERSPOILER**
Mucks with the continuity, though. Shysa was supposed to have thought Spar was Boba, and also Spar was Mandalore during that spell. Mandalore the Resurrector, to be precise. Shysa rallied to his call. *shrug*
The Wizards of the Coast RPG sourcebook "Geonosis and the Outer Rim Worlds" was where Spar first showed up. He was a rogue clonetrooper that was out there for an adventuring party to potentially encounter. His story was later expanded in the "Galaxy At War" sourcebook. Additional elements were added in the "History of the Mandalorians" article in Star Wars Insider #80. There are additional bits and pieces elsewhere, but minor.
--Jonah