Unquiet Dead

"You and Ganelon also managed to dig up some contraband books covering the topics your tutor left out... tales of the Unquiet Dead of the ice-lands, which left you unable to sleep for days and (when you recited some) sent your Keriatou cousins shrieking for more candles." -- Game One, Chapter One

At present, little is known of the Unquiet Dead.

Spoilers and Speculation
Unquiet Dead (spoilers)