Halsin in Baldur's Gate 3 is found as a prisoner in the Worg Pens, which are located deep within the Shattered Sanctum underneath the Goblin Camp. To reach him, you need to enter the Goblin Camp (west of the Druid Grove and past the Blighted Village), then go through the heavy oak doors into the Shattered Sanctum. From the main throne room where Priestess Gut is, head northeast past three "Sharp Eye" goblins and through a door into the Worg Pens area. There, you'll find several cages, one of which contains Halsin in the form of a bear, as he has used his druid Wild Shape to disguise himself

. Freeing Halsin involves either fighting or persuading the goblins, but there is no peaceful way to free him without hostility. If you manage to defeat all goblins in the Worg Pens without alerting the entire camp, you can rescue him quietly. Otherwise, a fight will ensue, but Halsin will aid you in his bear form

. After rescuing him and defeating the goblin leaders, Halsin will return to the Druid Grove and assist you with the questline involving the Druids and Tieflings. However, he does not become a playable companion until Act 2, after completing certain side quests