Nick,
Ultra Death
is made with Naga Jolokia, aka "Ghost Pepper".
Ultra Death is the hottest standard production sauce from Blair's, it's four levels hotter than "Pure Death", and the only things Blair makes that are hotter are the Reserve sauces - which, at $35/bottle, he can keep.
Ultra Death, Pure Death and the Reserve sauces are the only ones from Blair's that use Jolokias, the rest use other combinations of peppers.
Being that it only has four ingredients, Pure Death probably has a cleaner flavor than Ultra Death.
The Chile Pepper Institute at NMSU came up with "Holy Jolokia" which is, IIRC, a Lousania style sauce make with only Jokoias:
http://aces.nmsu.edu/chilepepperinst...l#anchor_59303
You can get it through CaJons:
http://www.cajohns.com/
CaJohns also sells Jolokia rubs and dried pepper pods.
Dave's (Dave's Insanity sauce) also has some Jolokia based sauces.
I'm going to attempt growing Dorset Nagas next year (there are about four or five peppers in the "ghost pepper" family, it's one of them, and is better suited to climate where I live).