Yuan Shu is an aged human man who was raised from the dead by Kandrelion around 1164, and forced to fight for him and defend his lair. He defied Kandrelion by only following the letter of his orders and not the spirit, and was rescued by the group, given some magical aid that reduced his age slightly, and given rooms in the temple of Balder.
He claims to know many martial arts, and to have mastered every one he encountered, before his death, several hundred years ago. However, he now says he desires only to rest and enjoy the few years of life he can now look forward to, and is not taking on students. He spends most of his time in the library at the temple of Balder, and is slowly 'attuning' himself to it, which will give him the ability to more easily find specific items, as he spends more time there.
As he no longer wishes to be treated as a martial arts master, he prefers to be addressed as simply a wise elder; in Shintapoor, most would call such a person Grandfather, and understand you were referring to him generally as 'wise old man', and not truly your grandfather. Might be misunderstood in Aertael; you could use the Shintapoori word, which is Mingzhi - thus, Mingzhi Yuan.
He claims to have been a teacher of the martial arts master Ji Gai, who lives on Wizard's Island, about 600 years ago.