In Norse mythology, Fafnir was the son of the dwarf king Hreidmar and the brother of Regin and Otr.
After Ótr was killed by Loki, Hreidmar received the cursed gold of the dwarf Andvari's as repayment for the loss of his son. Fafnir and Regin then killed their father to get the gold, but Fafnir decided he wanted it all, become a dragon (symbol of greed). Regin then sent his foster-son, Sigurd, to kill the dragon. Sigurd succeeded by digging a pit under the trail Fáfnir used to walk to a stream and plunging his sword Gram into his heart as he walked past. Regin, however, corrupted by the curse on Andvari's gold, planned to kill Sigurd to take the treasure for himself, but Sigurd, having eaten part of Fafnir's cooked heart, was warned by birds of Regin's attack and ended up killing him.
"An evil dragon of Norse lore. He was defeated by the hero Siegfried. In the Volsunga Saga, he was a giant wyrm that spat out poison."
—Shin Megami Tensei: Strange Journey Compendium
Fafnir appears as a random encounter enemy in Sector Horologium. He mostly appears in the basement floors and especially in the dark areas. His "mechanical dragon" appearance in this game is played up in an EX Mission where you can request a part from him, either screws, scales, or circuits, which will be made into a piece of equipment that you can use.