From The Heretic Knowledge Vault
Little is known about Rokku, since he's not appeared in the actual comic and possibly only exists in the Fun with Familiars continuity. Rokku is most notable for being Locke's owner.
According to FwF author Jim Hanson, Rokku attended the Sashi Mu Academy of Thaumaturgy and Conjuration where he was an honor student until his final year, at which time he was expelled under "complicated" circuimstances. The full details leading up to his expulsion have not been revealed yet, however will probably enter into the overall plot of FwF.