"If This Be Justice...!" by Lee and Romita/Ray. 20 pages.
Daredevil and Ka-Zar are downed by the mercenary Boswell, who hunts for Ka-Zar's half of the medallion. Parnival and his brother Ka-Zar each received half of a medallion upon their father's death, which together unlocks a secret vault which holds Vibranium (a name not yet invented, but called 'Plunder-Stone' by Parnival). Boswell works in conjunction with Parnival Plunder's butler, Feepers, and the two seek to steal the Vibranium. Parnival discovers the treachery and disposes of the pair, and now possesses both halves for himself. He recovers the Vibranium and creates a weapon from it and takes on the costumed identity of the Plunderer. Ka-Zar stands trial, wrongly accused of murdering Feepers by his brother, until Daredevil brings the Plunderer down and clears Ka-Zar's name.
First costumed appearance of the Plunderer.
Reprinted in Ka-Zar (1970) #3.