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

Hello everyone. Thank you for the tip. I defeated everyone, collected the artifacts, leveled up my heroes, and assembled a large army, but I couldn't get through the magic portal. And now I've done it: I placed 4 Necromancers together with Arnela on the altars. The gate opened, I captured Holyflame, although the enemy had a ballista that was mowing down my skeletons. But I still overwhelmed the enemy with the sheer size of my army. I completed the mission. Thanks again for the tip.