The Searing Collars you brought me are powerful demonic implements. Divining their origin is, I'm afraid, beyond my skills as a shaman. We will need a warlock to study them.
Take a searing collar to Arnak Fireblade. Although he is a skilled warlock, he professes to use his powers to thwart demons, and claims his research in the occult is benign. Be that true or false, we may need his aid against the demonic cult in Durotar.
You may find Arnak in Orgrimmar in the Cleft of Shadow.