Regulus Black

Regulus Black (? - c. 1980) was the younger brother of Sirius Black. According to Sirius, he had joined Voldemort, then panicked at the seriousness of what he was asked to do, and tried to back out.

It is likely that before Regulus was killed, he found the locket that Voldemort had used as a Horcrux. Regulus left another locket in it's place and on it was an engraving stating that he faced death so that when the Dark Lord met his match, he would again be mortal.