[lordpidey]

At approximately 5:10 pm EST 12/14/2021, I noticed a mirage desert BDP to the southwest of Alstalasia.

It is directly west and adjacent to the swamp.  Attempting to walk onto it failed, as though it were a solid object.

I have attempted to walk onto it from all directions except west and southeast, which are a mountain and ocean respectively.  The symptoms were the same for all directions.

A screenshot is below.

[adamkad1]

Its on top of the mountain!

[lordpidey]

Coming back later, indeed confirms that tile is normally unpassable and part of a mountain.

So that means BDPs are spawning on solid objects.

I hypothesize what happened is one spawned on the marsh, and was then pushed away from the marsh, and landed on the mountain.