You have attuned yourself to your black dragon ancestry and can poison foes with your touch.
Prerequisites: Draconic Heritage (black), sorcerer level 3rd.
Benefit: As a standard action, you can convert an arcane spell slot into a dangerous poison that you deliver by touch. At any time before the end of the same turn in which you activate this ability, you can make a melee touch attack as a swift action. The poison renders the target fatigued and deals 1d8 points of damage per level of the spell slot converted; 10 rounds later, the same effect repeats. Each time, a successful Fortitude save (DC 10 + the spell slot’s level + your Cha modifier) negates the fatigue and halves the damage.
Source: Dragon Magic, page 15.