Thules

A Thule or the Thules refer to members of The Thule Society, a subfaction of the Nazi who practice occult arts, specifically the dark arts and  experiments involving the dead. They have worked on the secrets of necromancy and have been engaged in a secret war against the Judah Initiative, a group of rabbis.

History
During World War II, some of the Nazis became interested and involved with the dark arts. They were particularly interested in reanimating the dead. They experimented on people they killed or prisoners of war, such as the jews. Eventually, the Thules managed to complete their goal and reanimated dead members of their group. All of their experiments and the results were recorded into a ledger, which they kept secret.

Their activities eventually caught the attention of a group of rabbis called the Initiative, who then waged a secret war against the Thules. The rabbis sent a golem to storm the encampment of the Thules to great effect, although the ledger was lost for many years and will not resurface until 2013. Commander Eckart, the leader of the Thules, managed to escape by performing a ritual a few minutes before the golem attacked him.

Sometime before the present, Eckart either managed to revive some of the fallen members of their society or to recruit more members into their society.

Present
In the present, the Thules, including the reanimated members, began to look for the ledger which they lost back in World War II. They intended to retrieve the ledger to keep the results of their experiments secret once more. They were led still by Commander Eckart, who was the sole survivor from the assault of the Golem on their headquarters in the past.

The Thules were keeping a close watch on members of the Judah Initiative and were capable of casting powerful spells. One of the Thules caused the old Rabbi Bass to spontaneously combust. However, prior to his death, the rabbi managed to hide the ledger somewhere in the local library. When Sam Winchester managed to decipher the code the rabbi left, the Thule assassin attempted to kill the hunter and the young rabbi Aaron Bass with a magical poisonous dart. Dean Winchester and the golem gave chase, and the latter managed to subdue the Thule, who refused to give up. The golem snapped the Thule's neck, lifting the poisonous spell from Sam and Aaron.

Commander Eckart and his driver Heintz then investigated the death of their brethren. Upon finding clay on the scene, Eckart realized that the golem and the Initiative were responsible for the attack. He later tracked and attacked the rabbi and the hunters and challenged Aaron for the ownership of the golem, which was incapacitated during the fight. Aaron managed to fight back, allowing Sam and Dean to kill Commander Eckart. Heintz managed to survive by hiding behind the golem before escaping through the front door.