Stuns, Knockbacks work on the the Sons. A DarkSim Hand of Rag works as a knock-back, but its hard to get since DarkSim only stays on Rag for 8 secs and you only get the HoR for 15 secs. Deathgrip works as well. Silencing an add right before it gets to the hammer works to stop supernova. Full Silence....example Strangulate/Arcane Torrent/Imp Counterspell.