The sverdhkottur (plural sverdhkettir), or "sword-cat", is the Thjodhiskmal name for the creature known more commonly in English as the "sabre-toothed tiger" - an animal long extinct in our world, and all but extinct in Midhgardhur, though the species is still known to be extant there. The sverdhkettir are known to be a highly cunning, intelligent predator, and when their territory conflicts with that of humans, one or the other must generally perish (hence their rarity even in Midhgardhur). However, on rare occasion, such creatures have bonded with a human or landvaettur as a companion. Such a sverdhkottur companion is never truly tame, but has simply adopted the human or landwight as part of their family.
Appears in: "The Gaeludyr" in Tales From Midhgardhur, Volume I
Source: Paleontology