Badass: Took on all the main Bronzies simultaneously in a brutal curbstomp. Shiryu almost resorted to Rozan Kōryūha but was stopped by Shura's spirit because it would have destroyed the Odin Sapphire. It was only after getting beaten brutally that Shiryu was able to find Siegfried's weakness that Seiya was able to change the tides of the battle. Even than, Siegfried still had such stamina and power that when Sorrento appeared, Siegfried not only pierced his ears in an attempt to nullify Sorrento's Dead End Symphony but was actually able to come within melee distance despite his injuries from Seiya. He even got pierced through the heart by Sorrento but Siegfried had the reserves and willpower to gather his cosmos and take Sorrento with him in a suicide attack similar to Shiryu's Rozan Koryuha. Sorrento would have died in the attack if he didn't use illusions to weaken Siegfried's grip enough to pull out his flute and play music to make Siegfried lose control and let go off him.
Combat Pragmatist: Since he has a weak body but quite versatile powers, he uses those and his knowledge without any mercy.
Crystal Prison: A nasty version. He can summon the "Amethyst Shield" —an attack that sends shards of amethyst flying from his body and towards the enemy, encasing him or her in a shell of translucent gemstone. If they're not freed, victims will be robbed of their lifeforce, and eventually become skeletons trapped in amethyst. And the only way to really free them is to kill Alberich himself. That almost happens to Marin and later Seiya, and Shiryu has to save them both via fighting Alberich to the death.
Self-Made Orphan: He snaps when Volker tells him that he murdered his biological parents and kills him. Little did he know, though, that it was a part of Volker's Thanatos Gambit: he wanted to both atone for the accidental killing of Mime's family and die in battle instead of his long-time illness, so he put on a Jerk Ass Facade for many years. In reality he always loved Mime like a son, and once risked his own life to get him medical attention, but due to his honor issues he could never show it.