I am sorry to report a big problem with the Hydra Hero.
He appears to domsummon at a high rate cavalry units(monster number 20). I was play testing Ctis with Epic Heroes and Worthy heroes 1.7 when the Hydra appeared at the gate. Soon thereafter, large numbers of calvary began appearing.
I moved my Epic Hero out of the province with all of the cavalry, and they continued to appear in the capital, where the Hydra was the only possible offender.
Screen shot attached:
