Osric is actually a canon character, one of those people that so little is known about that they make a lovely plot device for GMs. Osric is one of Benedicts two full brothers, the other being Finndo. They are known for having died for the good of Amber.
In terms of Dreaming in the Real, we first must understand what the Bright Pattern is. Cort uses an elemental template for the Patterns: Amber being the Earth Pattern, Rebma the Water Pattern, and Tir-na N'ogth being the Air Pattern. the fourth, the Fire Pattern, was Osric's Pattern. When Osric "died" for the good of Amber, he took the Pattern he had the greatest affinity for with him. The Fire Pattern, or "Bright Pattern" has been horribly warped, and now only the dead can walk it now.
Cort's original ideas on this also appear in an archived essay on the Amber List FTP site.