Skills for an Inferno hero.

and what does leadership give you?

When playing as Inferno, I usually choose a standard set of skills. I prefer to create a powerful army with the help of my hero, so that everything is useful in battle to defeat enemies and nothing interferes or distracts. My choice is Attack and Defense first, then I take Luck and Leadership. Luck is clear, it won't hurt anyone, but Leadership is especially important to me. I almost always choose it when playing as races with high initiative (including demons). After all, Leadership gives a noticeable bonus when it triggers - for each unit of morale, my troops get a 10% chance that their next turn will come 50% faster. Therefore, if the morale is at its maximum, i.e., 5, the army will be able to move 50% more often than without it! You have to agree that this is quite a lot! And for dessert, I usually treat myself to Dark Magic - it's so nice to cast a mass Slow spell and start tormenting enemies often with the help of Leadership and strongly with the help of Luck (it's like a real pleasure!).
This is, of course, a template for skills, so different options exist - you can take Logistics or Mechanics instead of Defense (especially if you are playing as Deleb), there is no clear scheme, I adapt depending on the specific situation...