you encounter a large group of goblins 'defending' this hole, while they issue combat barks about protecting the loot. afterwards, and only upon close inspection does the ? icon change to stairs. Note that this rewards a more active investigation, not just passively clicking it because "hey, the stair icon!". When you go into the hole you find a small mycoid lair with a dead mage sent from Suldanessar. The lair has some loot, but the mage's body has a note saying he was sent from Suldanessar to hunt the exiled or something. Nice tie-in to BG2 without beating you over the head with it. Irenicus's name isn't even mentioned in the note.
outside the hole there was also a human body with a bolt of polymorph into squirrel on it. A single bolt. I looked for a squirrel hoping for a secret encounter if I dispelled magic on it, but it either didn't exist or died in the melee.
aVENGER did I miss a secret here?