Heroes 5.5 WarGame Edition - Tactical Edition.

Mythology, after all... a dozen of "Tors" sounds strange.

But doesn't the fact that the devils are named after a Satanic god bother you? ))
They couldn't come up with better names for alt-tans than "Tors." "Earls" are constantly confused with "Jarls" (it's the same thing).
By the way, accumulating ten "Tors" with the WGE dynamics is difficult; it's like collecting 5 dragons. :)
The point is that 6th tier creatures are usually not numerous enough to include legendary creatures like Hydras. You can't gather many of them in an army.
Even 2-3 "Tors" are a serious enough threat to be taken seriously.

Regarding immunities, I simply didn't mention the neutral creatures; they have them too.