Inferno tactics.

Theoretically, you can take the Dragon Utopia on 112-113 with any Castle, but nonetheless, Inferno has the least chance of doing so, at least in SoD. It's a realistically weak castle, whatever you say.

It's only weak because its generator respawn is heavily deprived of resources, and the starting army is actually quite weak. And if you were born underground on top of that, you immediately want to surrender!

But in general, demonology is cool! I personally took a minimum Dragon Utopia on the second map in SoD with native troops - 66 demons (I had a cheat ring and a couple of caches). I lost almost all of them, true, but I took it :)