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Will O Wisp
Will-O-Wisps spawn in many starting zones, because of that they are the first monsters many encounter that require a magic weapon to deal damage to. Gratefully they are a peaceful monster so you are not forced to deal with a hassle of a fight if you don't have magic weapons. They are useful for their Greater Lightstones, which can be used as a light source, or sold for about 15pp to players.
They seem to be created from nothing more then animated light.