Okay now going by memory Fjalar has shadow bird and shadow monster. It happened when intense emotions are high I think it was high negative emotions and probably sins like wrath. First shadow form takes form like say lust or anger is very high peak. If the emotions are uncontrollable that is not very very easy to manage. Using thermometer as example, if lust is too high reaching to top then Fjalar become shadow bird. If the lust is very extreme that cause the thermometer to crack and explode then he turned into shadow monster [DeviantArt](https://www.deviantart.com/darkeye5000/art/Fjalar-Shadow-Monster-889495065)