Anointed by Emily, his service as a Slayer Dragon was unremarkable. He gained a reputation for prudence and dependability, being by nature a very cautious type.
He was not Emily's first choice to succeed herself as Pendragon. She outlived the individual whom she had groomed, and chose Tanner because she was confident she could trust him to find her a more capable successor.
However, Tanner was already elderly when he took up the sword, and his cautious nature made the choice very difficult. He took ill, and on his deathbed passed the sword to Orin, who had also been anointed by Emily.