This is a heavy stainless steel chain with wolf head ends holding the loop of the Fenrir pendant.
In Norse mythology, Fenrir or Fenrisulfr is a giant wolf. It is the son of Loki and the giantess Angrboða. Fenrir was tied up by the gods, but was destined to grow too big for his bonds and eats Odin during Ragnarök. After killing Odin, he is killed by Odin's son, Viðarr.
The chain loop is cleverly designed to open easily when needed but secure so as to not open by mistake when on.. the chain is a box chain made out of stainless steel and the pendant is made out of pewter.