Tales say the dwarves fled deep into the Underdark from their Derro pursuers. They ran and ran, and sometimes hid, but ever onward they moved. An every so often when they chose to slow or stop, they would hear it. The howls of Death dogs. The slapping paws on the cold stone. The slathering of jaws and the persistent sound of a tongue dragged across tooth. Coming ever closer. The dwarves ran on, into the dark. Through caves long abandoned, knowing that Derro were hanging just behind.
At one point, they were able to lay a trap for the pursuing hounds. Caught off guard and surrounded, the animals were finally unable to simply flee, and were forced to fight for their lives. In this moment the dwarves slew them, and gained themselves a moments reprieve. A moment to sit, talk and be still. In this, the companions noticed for the first time that one of their number was not entirely as they had once known him. Changed in more ways than just the skin on his back. He seemed distracted but happier. Lighter. As if he was in the company of people that made him feel safe. Even in this darkness, deeper than any other. An more disturbing too was his tendency to talk past his companions. As if the words he was saying were meant for ears other than theirs. All cogent words, that in context made sense. An yet, spoken around or beyond the dwarves in his company.
Confronted on this, the dwarf would admit he saw his family with them. He knew they were not there, that they were but figments of a mind pushed too far. Yet he could not shake them, an it was not easy for him to remember they were not present. Not without something more important to focus on. Asked what that was, the changed dwarf would go quiet, and then talk of his family. He would talk of his brother, an of his quest to uphold the family oath. He never truly elaborated on what the oath was. Just that it had gotten his brother killed and that all he had left of him was the shield he now bore.
The dwarf would talk at length of his family in these few quiet moments. At least, he would when asked about his hold on reality. Always he would be sure to acknowledge they were dead. An yet sometimes it would seem he was describing a person he was looking at. It was uncanny at best, and uncomfortable the rest of the time. The others were not pleased with this new turn in their wayward companion, but as yet they had not had the resources to help him recover.