I personally like the spell infernal, especially if you have a fire shard or two. One shots entire groups of monsters with one cast.

This game is incredibly easy right now, i have no idea what you're talking about.

same here, only played on "normal" so far, but well the AI has way more troops and everything, but they are cannon fodder, especially to my archers

I was saying how easy the AI is:

https://forums.elementalgame.com/397414

Attack them early.  You can wait for them to expand and then pounce.

Probably you want to have three to five cities up quickly, then in the military tree be able to make squads of four, then have 2 or 3 equipment upgrades, and fortifications never hurt, then make sure you have at least a couple squads of guards in the cities getting hit with AI spam (and at least one squad of peasants elsewhere), and then you can sit back and look at the line of attackers as an easy stream of gold revenue.  All of the pop-up windows get annoying whenever you get attacked, which can be several times a turn, but that's all.  If you can defend your cities okay, you can then take your sovereign and some elemental giants into enemy territory and start knocking down your opponents economy.  That would be a fairly typical game for me.

I also notice that if your economy is weak at the start, multiple AIs tend to gang up on you.

That said, dealing with AI spam early on does kind of cut into any adventuring and exploratory aspect of the game as you have to focus on military victory.  I wish on easier difficulty levels the AI might be a little more passive and focus on building up and researching.