Stingtail advances personal quests for both The Red Prince, and Sebille through allowing them to converse with him.
You can save Stingtail from death if you attack and defeat Silence, and this will not cause Griffs crew to become hostile.
If you tell Griff that he stole the oranges, a unique NPC "Silence" will be seen attempting to murder Stingtail on Griffs orders the next time you go to Stingtails shack.
Stingtail is the one that stole Griffs "oranges", can be convinced to give them up to any character with two points in persuade, as his highest skill is fairly low.
Is a Pyromancy vendor, for base level pyromancies.