First, the hero attacks solo, defeats the genies, and runs away. Then, single genies and 80 medusas with 17 vampires; the medusas almost took them all out one by one. There were between 6 and 9 of them, I don't remember exactly.
I don't know how difficult it is; there are sorceresses, genies, and mages; the army is fully upgraded, I'm going down now, but it shouldn't be too difficult.
https://c2n.me/4crmIPp
I also have 54 ice demons and 707 halflings in reserve. I'll have to sacrifice some to the dragon golems, or maybe take more demons; there are 3 devils at the bottom.