uh.... I don't remember :'D it's from a quest with elyana, when you talk to her in the dormitory you built for her, she may give you a quest. Red dialogue box as usual, she wants a pet like yours
I am not sure though.... you probably already accepted the quest. If you did, go to the mountains then select other places. Go to the cave if that's an option
I am assuming you have the tentacle "pet" since it's part of the main storyline