In essence, there is nothing special about taking the city, but when attacking a city, the Obsessed often goes first. Place him in defense. As soon as the paralysis from the Baroness wears off, start attacking the enemy with the Obsessed. If he misses, put him back in defense (unless it's Trolls and other opponents with an attack of over 120). As a result, the Baroness often gains a level, and sometimes the Obsessed does too. The appearance of a Berserker in her unit will noticeably increase her potential as a secondary hero.
Even when playing on a high difficulty level, the Baroness rarely misses, unlike the Banshee. And if you give her a buff/elixir for accuracy, even 10% will increase the hit rate to 88%, which is quite good. =)
P.S. You can also capture Ruins in a similar way. Good luck!
Added 14 minutes later
Tactics on a small map against the Human Empire. Leader-warrior, if the Empire has a similar one. Goal: Develop a unit to level 2 in a short time.
The development is the same as described above. The main task for the first few days is to develop the Zealots into Wizards. Thus, when equal-level units clash, the Legions will cause a lot of problems for the Empire with 30 damage to all (mass healing from the Priestess = 20). After making the first Wizard, replace him with a Zealot and make a second Wizard. Then, develop the leader and the Imp. Even with one Wizard, the chances of winning are quite high. The appearance of a Demon in the unit with an attack of 80 will increase them even more.
You can develop the Wizards into Dopplegangers or Demonologists.
Problems - two archers in the Empire's unit. Countermeasures - develop a Gargoyle instead of the Imp. When attacking, use protection potions and magic. Try to scout the entire territory faster than the enemy to avoid an ambush.