Those Who Prevent the Extermination of the World Tree

Those Who Prevent the Extermination of the World Tree (世界樹を絶やさぬ者) 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, Those Who Prevent the Extermination of the World Tree, together with the Iron Stake that Carves Knowledge, 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
Those Who Prevent the Extermination of the World Tree was noted to have been active recently by the Tour Guide, around the time of the bombings carried out by the magician Leasic. It was crushed when Brunhild initiated her revenge against the five cabals.