"The Will of Ashan" - "Heart of Darkness" [2nd campaign, 5th mission]

Don't worry about me, maybe someone else will come and give me some advice, and I've already replayed this mission three times, it's a shame that it's been unsuccessful :(
But on the third try, the hero had 43 liches by the second week :D

I'm replaying because I'm curious myself, after the first two turns)).
In the first turn, I hire necromancers in the castle tavern: the hero Naadir - level 1, and in the second turn, two more: Kaspar - level 6 and Ravenna - level 3. In total, Arantir, Ornella, and three from the tavern. That's four necromancers + Arantir to perform the ritual.
I'll try to complete it later, but when I played, everything went smoothly without any problems.