After accepting Fragments of the Orb of Orahil and having the sub quest open i completed Shard of an Infernal but upon turn in wasnt rewarded the item to complete Fragments of the Orb of Orahil character: bènafflock realm: PVP
Okay to answer your question, you do not get the Infernal Orb from doing the quest "Shards of a Felhound/Infernal" you get them from killing Burning Blade Summoners in Desolace.