Necromancer – “Invasion” [Campaign 3, Mission 3]

I also had a mission skipped when I was playing the pirated version.
Now I'm replaying everything on the licensed version, and this mission didn't skip.
Damn, there's a garrison with 20 Titans.
I've already taken 2 artifacts, cursed 2 towns, and defeated the elf army.
Where should I attack next, towards the 3rd town?