The material below is Open Game Content from a 3PP Source
Stench Musk (Ex): An eidolon can spray a cone of musk similar to a skunk’s. The eidolon can spray a 30-foot cone of musk; those caught in the area weapon must attempt a Reflex saving throw (DC is equal to 10 + one-half the eidolon’s HD + the eidolon’s Constitution modifier) or be sickened for 1 minute per HD of the eidolon.
Creatures that fail their saving throw can be tracked more easily with the scent ability (lower associated skill check DCs by 5), until they have been thoroughly cleaned (requiring 24 hours, or a Heal check with the same DC as the stench musk’s Reflex saving throw DC). The eidolon can use this ability once per day. The eidolon can use this ability one additional time per day by spending 1 additional evolution point (maximum 3/day). The summoner must be at least 5th level before selecting this evolution.