Evil Spirits are souls with the appearance of a ghost in MegaMan Battle Network 6, which are capable of creating barriers to areas of the Net. The awakening of the Cybeasts has caused these Evil Spirits to swarm the Underground and then, all over CyberNet.
To break the barrier in one area, player (MegaMan or depends on which Navi do the player choose) must first exorcise those spirits. They can only be fought using the "SoulWeapons" which an officer gives to MegaMan at the beginning of the scenario. The weapons are SoulKnife, SoulSword, SoulAxe, and SoulGun, each having a different range. If attacked but not destroyed, an evil spirit close to player will strike back, dealing damage. Note that if an Evil Spirit is attacked from behind, it will die immediately.