Fortress versus Necropolis.

Here’s a rough outline of a strategy that can be used to counter a high-level Dwarf, even Ingu. First, choose a hero. We’ll go with Deirdre. You need to level up her Spell Power skill and acquire various artifacts that reduce enemy Spell Power, Initiative, and Luck. Next, get the appropriate upgrades. Gather as many Banshees as possible and protect them at all costs in the final battle. Make full use of summoning. Phoenixes, elementals, and Celestial Shield are our allies. Invest heavily in defense and acquire a couple of Sar-Issa items. Don’t shy away from using Plague and Subjugation spells either. With low Spell Power, the Dwarf will not only miss turns but will also be heavily attacked by summoned creatures, Plague, and other units. Quickly blind the Jarls and focus on the dragons, which will be dealt with by the Banshees, Phoenixes, and Zombies. You shouldn’t have any problems with the rest.
This tactic has been tested. Even the best artifacts won’t help the Dwarf.

However, there’s a downside: you need a lot of artifacts, spells, and a mentor.

There’s a second approach. Take Zoltan. He blocks antimagic, allowing us to subjugate the Jarls. But this isn’t a perfect solution either.