I think the other guy lives in that underground temple, which is where Locke took Ben, summoned the smoke monster and basically convinced Ben to do whatever he said.
Also, note that the hut that Bernard and his wife build in the forest is what ends up being "Jacobs" hut that Ben takes Locke to and pretends to hear Jacob, but they never really say which of the being lived in the cabin, whether it was Jacob or the other guy, which they conveniently left unnamed.
In one of the Episodes, the one Ben was talking about, where they are in the Cabin and Ben is trying to fake seeing Jacob but Locke actually heard someone say "Help Me", we learn that something was definitely in there at some point.
It could be that one of the deities was trapped inside, was it Jacob? (the ash around the cabin had also been broken) The "Good Guys" certainly seemed fearful of what might be inside, they never say who is supposed to be in there, just that "He" hasn't been there a long time.
The first time we see Jacob though, he's in the exact same room they find him in at the end, so I think it's unlikely the cabin was his.