Floor 3 has a single one-arm Notorious Monster Acrolith normally present in one of the first three rooms on the east side. It can be "broken" down to 2 legs by critical hits or job abilities like Box Step and Violent Flourish.
Floor 4 north and south each have two one-arm non-NM Acroliths.
When they are defeated, a third two-arm Acrolith (Notorious Monster) will spawn.
Floor 4 has two non-NM Acroliths present on both the east and west sides. Regardless of the side, defeating both Acrolith will spawn the Acrolith NM in the room which contained the second Acrolith. Design plans dropped differ depending on the side.
Acroliths are spawned from each of the final 5 Archaic Ramparts present. An Acrolith will only spawn from a rampart if it is linked with another rampart. If it is aggroed or an offensive action is performed first, a substitute monster will be spawned.
