Its very hard to get this ultimate skill, so inferno is usually weak, but thats the case, because if you get urgash's call and, additionally, inferno artifact set, and you have leadership with gate master and luck with gate swarm or expert summoning for tier 7 creatures phantom forces, you can multiply your army infinitely and in an instant. Didn't I mention about 2-3 towns with hellish looms? No I didn't, so, technically, your army is for real 5 times cheaper and 5 times more numerous than anyone else. IMO inferno is strongest - no wonder why every campaign depends on united armies against demons.
Getting ultimate skills is typically not done in regular H5 play due to how you'd want other more useful skills. Inferno also has a weak early game since Horned Demons are crap (low damage, low initiative).
@@marvinf8128 It is almost impossible to get ulimate skills during campaign, especially in Basic game and Hammers of Fate. It is easier to get that in Tribes of the East, but still - building your hero based only on getting ultimate is a huge mistake.