Budkhul-beken is a poi that you can't get to easily. You can see this landing up on the wall in the Redhorn Lodes. You have to to Nud Melek and then come back into the Redhorn Lodes down the other path you see at the top right of your map.
On my way over to this poi i actually got the location for Sigin-tharakh in Nud Melek. It counted for the deed. it is north of the campfire on the map, and in the middle of the two small streams of lava. Location 10.1S and 101.1W
Hope this helps,
Shameze