The third quest step says to Create the Ultimate Blight Antithesis Power Source and give to Nerask.
There is no such item. Instead, its the Dormant Stone of Antithesis, item 123054, that is created and to be given to Nerask.
Not to be confused with the Ultimate Antithesis Power Source, item 123052. This is created by combining the various blight power sources plus the residue. This item is not handed to Nerask...instead, its combined with the seven antithesis clickies to produce the Dormant Stone.