The Giant Grey Grendels are a breed of Grendel designed for Creatures 1 by an unknown breed maker. They occupy grendel breed slot 3.
They are only downloadable in an archive.
(14 Jan 07 - The above link didn't work for me so I'll link to the page and you can click on the download from there. http://www.creaturesforum.de/nornhome/page.jsp?user=malkin&page=1057742036233.xml)