During the Dawn War, the Gods marshaled champions from among the mortal races of Tol. Some chose a path of healing and protection, but some were imbued with the very words of creation on their tongues. These powerful champions became known as Invokers.
Unlike clerics, Invokers sometimes choose to serve not one god, but all deities of their pantheon. They consider the connection between the various gods, even the evil ones, to be more important than any petty squabbles, and, for them, the threat of the return of the Primordials remains real and present, rather than something hidden in the past.
Invokers can come from any walk of life, though they are far more common among those races that revere a pantheon of deities.