Troll cross

The Troll's Cross (loosely translated "Troll's Cross") is the symbol most often used as an amulet, made from a circle of iron crossed at the bottom. The amulet was worn by the early Scandinavian peoples as protection from trolls and elves. Iron and crosses were believed to help ward off evil creatures. This sign has a visible resemblance to the othali rune.

quote from Wikipedia:

Although widely considered (the symbol is the Troll's Cross) part of Swedish folklore, it was created by Kari Erlands as a decoration sometime in the late 1990s. It was alleged that it was copied from a protective rune found on the parents' farm.