Ok, so there is this tombstone in the Underdark dedicated to the memory of Myrna the dog. I learned about the existence of this quest by accident from the internet (I knew that this quest exists and that it has something to do with the Arcane Tower, but that's it). I toured the entire Underdark level without finding it. So I got really stubborn trying to find it. Started strolling through the underdark again. I killed every single monster in the dark like a murder hobo searching for this tombstone believing that it must somewhere close. Nothing. Finally when the Underdark was cleared from all the monsters and other quests I decided to do another solo walk to try to find it. And there it was, I found it! Yay! So then I started to search for the shovel. And in the process I lost the tombstone again. Somehow I was able to retrace my steps and I came back to dig up the dog. MC spoke a line of dialogue about the strange runes on the dog's collar, so I assumed the collar is in my inventory. I headed to the Arcane Tower to check how the button will react to the collar. But I realized I don't actually have the collar in my inventory. So I had to trek all the way back to the tombstone but naturally I got lost... again. Aftter a while I FINALLY FOUND THE TOMBSTONE AND THE COLLAR. I came back to the Arcane Tower and put the collar on (Astarion was probably was very pleased by it as much as the rest of team) and I pushed the button. And it return for all my efforts I got a raw steak. It was a dog feeder that reacted to the presence of the runes. MC is standing beside the steak and I couldn't believe what just happened. The end.