Sevastian Guile was the younger brother of Gavin and Dazen Guile, and the youngest son of Andross and Felia Guile. He died at the age of eight when he was killed by a Blue Wight, leading Dazen to harbour a lifelong hatred of Wights and a desire to exterminate them.

Dazen described him as "everything that was good about [Dazen's] family with none of the bad."