in my opinion, Inferno is possibly the most original faction. In terms of abilities and troops. Specifically, the portal, hellfire, a small number of flying units and archers. You have to put in some effort to win. And I like challenges;
dwarves are also original, but their runic magic is nothing more than simple magic, but it consumes resources instead of mana.
Sylvan's "Avenger" is also an original ability, but it is very difficult to implement. That's a drawback.