In case you want a hint on finding the entrance to the Underdark;
Start searching in Priestess Guts' chambers inside the goblin camp.
Thanks.
I had spoilered that for myself when looking for a solution to my "problem".
Yeah it's apparently when Halsin lives that he gives directions to the Underdark... given that it's pretty easy to have him attack you though (I found, personally), this still looks like an oversight on Larian's behalf. You shouldn't be able to travel to the Towers maybe, but at least have some conclusion of kinds. As it is, going this route seems "incomplete".
