Total War: Warhammer III

You can get this unit from the blueish-purpleish building chain called "Grand Ur-Szalas" at level 5. That means you have to have a settlement of level 5 to recruit them. For Kislev that means either in your starting capital or in one of the other two big cities of Praag or Erengrad. Erengrad can grow the quickest, because of it's harbour. Also the building chain starts at level 3, so you can start building then.

To quicken the growth of your cities, concentrate on the green building chain "Ungol District" and "Guild District", use the "Salyak" Invocation of the motherland and built the "Temple of Ursun" in Kislev.