The first external sign of melange-induced metabolic change is visible in the eyes, as the drug tints the sclera and iris to a dark shade of blue. This level of extreme and extended exposure causes their bodies to atrophy and mutate over time, their heads and extremities elongating.
Also, they were notorious for participating in massive spice orgies. To enable their prescience, Guild Navigators not only consume large quantities of the spice, but are also continuously immersed in highly-concentrated amounts of orange spice gas housed in large tanks. Guild Ambassador in Cryos 'Frank Herbert's Dune' Physical Description
