Haven – "Everything is mixed up, truth and falsehood" [Campaign 3 – Mission 2]

I'm playing on normal difficulty. I approach the Necropolis castle on day 3, but I can't seem to win. I have 70 Guardians, 45 Archers, 15 Adepts, 6 Griffins, and 15 Cavalry. The enemy has 45 Zombies, 64 Skeletons, 44 Ghosts, 12 Liches, 14 Vampires, and 10 Lamassu. No matter how hard I try, I get defeated. Out of frustration, I tried playing on auto-battle, and the result was the same. Maybe I'm rushing things, and I need to recruit more neutral units?