Uncle Gray is the uncle of Sylphiel Nels Lahda who lives in a small mansion in Saillune with his wife, Maria. He's described as a middle-aged man with chestnut, white-streaked hair. He has a married son named Toran.
Gray also seems to have a job at the Temple of the Royal Palace as the head physician at Saillune's mystic infirmary.
He first appears in the fourth novel when Sylphiel goes to live with him after losing her family. Despite this, they are not very familiar with each other because the last time he saw her was when she was a little girl. At first, he acts uneasily towards Lina and Gourry because he is suspicious of them. However, this is only because he was given the job of hiding Philionel El Di Saillune in his home after Phil caught wind of an assassination plot on his life. Gray reappears at the end of the book where he is happily running his busy infirmary. Gray does not appear in the anime, outside a brief indirect reference to him in episode 23 of Slayers NEXT.
In the TOKYOPOP translation, he is erroneously called Sylphiel's grandfather. This mistake was caused by the fact that the words grandfather and uncle are greatly similar in Japanese.