Round table

If the treasure on the swamp contains angel dwellings, then the Pandora's Box will give, for example, fanatics or knights. If the treasure contains mummy or nomad dwellings, then the Pandora's Box can even give super-dragons.

That's right. Also, for the quest artifact found in this zone, you can get an army, and it will be of the same type. Often, you get something decent for some worthless artifact.
Last time, the treasure turned out to be Necropolis-themed. Besides other things, they gave a bunch of weak units for 10-19 green dragons (+hive +arena). For the quest trinket against forgetfulness, the old man at the house gave 10 Necro-knights.