You need to kill one of each undead enemy (excluding bosses) with a Flame Core attack; there are four Flame Core sub-weapons, but just stick with the one named Flame Core. Make sure you get the finishing blow with this weapon equipped. Fallen - Mount of Idols challenge, section to the left where you start. Fallen Warrior - In the same area as the Fallen enemy. Bones - Mount of Idols challenge, found at the Y-intersection to the right from where you start. Bone Soldier - Mount of Idols challenge, take the left path at the Y-intersection from the last enemy. Jump on the rocks and climb the wall, then go back down, jump back over the rocks and they will spawn. Bone Warrior - From the last enemy, climb the wall that you climbed before and it will spawn at the top of the wall. Skeleton Soldier - From where you got the Bone Warrior, continue climbing up to the next section. Skeleton Warrior - Streets of Argos, in the second area (street-like area). Skeleton Mauler - Same area as Skeleton Warrior Skeleton Archer - Same area as Skeleton Warrior Bone Archer - Streets of Argos, right at the very end of the place in outside part of town Bone Mauler - Same area as Bone Archer Death Soldier - Argos Castle Area, in the first outside area with some steps Death Mauler - Same area as Death Soldier Death Warrior - Argos Castle Area, in the area past the previous two enemies Death Archer - Same area as Death Warrior Dark Archer - Rare spawn that's in the same area as Death Warrior. Go to the area that's outside the castle, then go back inside and see if it spawns. If it doesn't, keep doing so until it does. Dark Soldier - Rare spawn in Medusa's Temple. Go to the big round room, and take the left exit. You will be in a room with a totem in the center, so take the left exit and go all the way down until the next room, which should have some water in the middle. This is the room where you'll find the Dark Soldier, so keep going in and out until it spawns. Lost Spirit - Underworld or Miasmic Swamp. In Underworld, it's right next to where you first climb up. In Miasmic Swamp, it's in the same area as the Dark Spirit. Dark Spirit - Rare spawn in Miasmic Swamp. Go across the bridge and drop off to the left, going into the next section. Stick to the left side in this new section, going down that path until you get to the jumping part. Go left on the jumping part and climb up the rocks, and you should see some Lost Spirit enemies; this is where the Dark Spirit spawns. Soul Eater - Found in Miasmic Swamp or Underworld. In the Miasmic Swamp, it's in the same area as the Dark Spirit. In the Underworld, it's in the same area as the Dark Soul. Dark Soul - Rare spawn in the Underworld. Go through this area until you reach some stairs that go to an area that has a lot of skeletons and some worms. Go back down the stairs and look back onto the highest ledge; this is where the Dark Soul spawns. You can refresh the spawns in the previous area by going to the top of the stairs and then back down; keep doing this until it spawns. Sightless - Norn Mountain. Go through the first section and into the next. When you come up to a T-junction, go straight and go into the next area. When you get to some crossroads, take a right and follow this path until you get to a dead end; this is where the Sightless spawns. Living Dead - In the Underworld, just before you climb the first wall.