As for whether Psihhh will be the first, we'll see.
I defeated Fenov differently. I gathered about 500 skeletal archers, protected them with one ghost each, although I had fewer than 78 ghosts compared to Psih, I cast Berserk on them, which affects two squads at once (gradually applying it with Kaspar), a general slow effect, and then on all the remaining ones. After the first deaths of Fenov (resurrection), I cast the Sorrow spell on each of them, and then I cast the Devastating Ray spell on the last squad until its defense becomes zero, and then I kill them with archers dealing 32 damage with luck, and I raise the fallen ghosts.