Go to the Zertinan Cavern, which can be reached through Nam-Yensa Sandsea, Ogir-Yensa Sandsea, Ozmone Plains, or Dalmasca Westsand. Go to the center of Asroza Sandflow (this area is best accessed through the Dalmasca Westersand) and you will encounter the Adramelk Boss. Defeat the Boss to get the Adramelk summon.