Posts from All castles in Heroes 3. Auto-translated

I disagree! There are usually a lot of skeletons, but other undead units are quite weak (in many parameters). Exceptions:
1. Vampire Lord
2. Lich
3. Black Knights.
Perhaps elemental units are good against the undead (vampires don't drain life from them). And they also have a good growth rate.

Message from celt
perhaps elementals are good against undead (vampires can't drain life from them).

You simply don't know how to play as undead. No matter how much you slow down three thousand skeletons, you'll lose if you don't have three thousand skeletons yourself.

The undead are invincible, especially Galtran. He can only be defeated at the very beginning or relatively early in the game... otherwise, as mentioned above, 3,000 skeletons are equivalent to a victory. Galtran always gets Air and Earth, so using two spells – either Haste or Slow – will help defeat him. Blindness doesn't work on skeletons, so you can't cast a lot of spells and then shoot them down... the skeletons will simply approach (either they are hastened, or you are slowed).

but if there's no other option...???

In my version, the lightning also hits a maximum of 5 units, but Solomir hits 6, and if you hit the central unit, the chain will go in different directions.