This, along with Arcane Disjunction Aura, are rewards from Don't Fear the Destroyer mission, given by Algera Shinglebolt in Brell's Rest. To get the quest itself you have to do the three prequests Gnoll Who Your Friends Are, Clash of the Kobolds and Gnoll with the Punches which all three begins at Berrina Saltidnarik, also in Brell's Rest. I however do not know if the prequests are needed to get the spells. You only get one of the two spells though when you do the quest, I've only done it once so far so no idea if you can redo it to get both spells.
