Blue crystal

My dad played it, and he said the following (he played your mission, and he really liked the battles; everything else related to completing the quests is complete garbage, especially the cart with the golden dust, which a commoner simply cannot find in their entire life on this map, as well as the rooms with two entrances that can be accessed with keys, but yield completely different artifacts – it's complete nonsense. He didn't continue playing because he realized that there would be another trick or flaw further on).