From Destinypedia, the Destiny wiki
A Nessus Token is an activity token that was rewarded from completing Public Events, Adventures or Lost Sectors on Nessus. They could be exchanged to Failsafe in the Exodus Black for various Emblems, Shaders and Nessus-specific weapons and armor sets.
Since the release of Forsaken, Tokens were rendered obsolete and are now unobtainable.
List of appearances