Skills for an Inferno hero.

Even the developers are obsessed with this unimaginably banal "good is stronger than evil" and other nonsense. There shouldn't be any bias at all.

+1. In both the third and fifth games, the demons aren't that great. In the fifth, they're much more interesting, but still... there's too much hassle with breaking through defenses, and the hero selection is not ideal.

I read your level 40 Nimue build, I was just searching for how much bonus the specialization gives, and I came across your post. It was informative and helpful, thank you.)

Regarding the build - a small nuance about the defensive perk. If you're going for light magic, this perk is definitely the way to go; it will make breaking through defenses much easier, and if you're focusing on dark magic and summoning, extra base survivability won't hurt. I had a battle against Nimue for Axel on the 3rd month, and the demon only won because of mana and the ability to control paladins.

I want to test one strategy against aggressive factions, specifically elves, who demons have trouble with, although it can be tried against anyone.

The idea is to take logistics and keen mind, light magic with stone skin and storm shield, standard attack, luck, and either a defensive branch with defensive posture or even stubborn defense or readiness (a very debatable perk for a demon, but still).
You'll have to sacrifice surprise attack (not a big deal) and either pathfinding or fast gate opening (in my opinion, the former, but it needs to be tested).

An important point - artifacts should not be chosen solely for their defensive properties.
Ideally, you'd want the dwarf set, which gives stone skin and dodge on expert, but if that's not available, then:

- Dragon's Tongue and Dragon Ring - together 4 defense (if there's no Inferno Staff), if not, then "On the Edge of Balance":
- Dwarf Shield and Cuirass - together 8 defense and 40 percent resistance;
- Maybe Sandals of the Saint and Secret Protective Cloak, although there are better options - together 2 defense. In total, 12-14 defense.

In upgrade locations like arenas, don't choose attack, choose defense. Many people (including myself) automatically choose attack and end up with a berserker with stats like 35-5-10-15. But we need to try to create something like a dwarf, something like 20-20-10-15, all numbers are approximate.

Battle algorithm.

First, cast stone skin on the hero with keen mind (if you don't have the set) and summon, then stand in defensive posture and buff the troops. Of course, not all the time, only until the gate is summoned. Then attack with the entire force.
The idea is that the troops should withstand the initial attack due to their starting defense and the applied skin, and retaliatory strike will compensate for the lack of attack.
If summoning isn't an option (you only have time to open the gate and then get hit by everyone), immediately attack with the troops under stone skin. It's hard to say for sure, as initiative varies depending on the artifacts, and there's also a 25 percent variance.

You can also try it without light magic, with the mass skin perk in the defensive branch, or you can try using keen mind to cast mass slow or immediately bless-retaliatory strike; variations are possible.

It might turn out to be nonsense. Or reinventing the wheel, as the game is quite old. But maybe someone will find the idea interesting. Or maybe someone has tried it, let me know the results.

P.S. I think taking defensive stats for a demon is the optimal option, in any case. Initiative and good damage, combined with survivability, should give good results.