Murmur is an incredibly powerful elemental born when the Universe was created, about whom little is known. The Shadow Council inhabiting the Shadow Labyrinth summoned it for their nefarious purposes, but seem to be having trouble keeping him under control. Its history is briefly documented in the Codex of Blood, which reveals Murmur is the primordial essence of sound. -wowwiki.com
guess hes been around for some time and isn't related to the Elemental plane :/