Originally Posted by Unregistered
the tick is that you have to wear little to no armour and hit it once the keep use pincushion until he dies but I think you should train passed level 15
Here's what I did. I went to Gerzuun alone, my main being a lvl 30 Paladin. I got rid of adds that came with the Infernals using Gigagash or Gigaslash (Omnivocational Swordmaster) hit the infernal armor once, then waited out the rest, pin-cushioning every turn. Also, make sure that you're wearing no armor. This method took me about 10 minutes to complete.