Skills for an Inferno hero.

The damage itself isn't that important here. The main thing is the effect of reducing defense by half. Devastating Ray looks weak in comparison. Of course, there are a lot of cool spells in the Darkness school, but physical damage noticeably increases after Fireball, and the question is which is more useful (probably depends on what Darkness spells are available in the guild).

Super ability is not needed for Demon Lords at all. I think they need skills like: Dark Magic, Light Magic, Luck (Wide Gates), Sorcery (Distraction), and something of your choice, for example, Attack. It is definitely necessary to manage to take Light Magic.

But why would a demon need Light Magic? Where would he get spells for it? It's not worth relying on Light Magic or a neutral castle. Sorcery is also not a very good skill for a demon; he is a warrior at heart, and one magic skill is enough for him. Besides, Distraction, in my opinion, is not such a great perk, and you have to invest in two not very useful skills.