Iron Stake that Carves Knowledge

Iron Stake that Carves Knowledge (知を刻む鉄杭) was a Norse Magic Cabal, one of five who united to attack Brunhild Eiktobel's cabal and were subsequently destroyed by her in revenge.

Background
Five years ago, the Iron Stake that Carves Knowledge, together with Those Who Prevent the Extermination of the World Tree, Champions from the Sea, Those who Know the Rune of the God’s Sword and the Hammer that Tempers Gold within the Earth, attacked Brunhild Eiktobel's cabal out of fear that her nature as a Saint and Valkyrie would cause pure Norse-style magic to go into decline.

Toaru Majutsu no Index SS: Kanzaki
The cabal was attacked and crushed when Brunhild initiated her revenge against the five cabals.