The Return, Part 2

On the snowy map, there's an ascent from the clearing where the mentor is. The road leads up the mountain, and at the top, you can see angels. I started climbing the hill, and it gave me advice to collect the relics of Sar-Illam. I already had the complete set at that time, but for some reason, it didn't mark the completion in the list of tasks, where it's listed as a secondary objective. And I didn't receive the quest to find the passage in the mountains; where should I get it?
But I'm playing as Necropolis, on Veteran difficulty, and I managed to defeat them anyway. I tried to get past the hill but couldn't, so I went back, gathered my army, and went down, defeating the undead...