Ryker Slade is the leader of the Arch Mages. His plans involve toppling the kingdoms of the world one by one, until they are all under his control. Meanwhile, he seems to have another plan for the peoples inhabiting the world, though it is unclear whether he intends to rid the world of all Mages other than the Arch Mages, or destroy all non-Mages. Both ideas are discussed by other characters throughout the series.
Only one Mage, Gabriel Lenis, is strong enough to stand against Ryker and the other Arch Mages. In an attempt to keep Gabriel out of the picture, Ryker commissions Nolen Novacula to attack, capture, and enslave him with a Castrofax. This has a double purpose, since Gabriel can also help Nolen retrieve the Silex, which he needs in order to bring his colleagues back from the dead.
Ryker suceeds in aquiring the Silex and uses it to bring the other Arch Mages back to life.
Later in the series, it is revealed that Ryker is actually the Element of Spirit, which is one reason he has remained alive so long.