Barghest

Golden Age Origin
Sir Giles of Clewsby was an evil knight and enemy of King Arthur. Through the magic of the sorcerer Black Barton he could transform into the Barghest, a "fearful night-beast." Those who were bitten by the Barghest were cursed to that they would gradually weaken and die within six hours. Black Barton followed him around and forced his victims to come to Clewsby Castle and swear fealty to him in return for having the curse lifted. At Black Barton's behest, Sir Giles took on the Silver Knight in single combat and, taking advantage of his refusal to wear his enchanted armor in a tournament, transformed into the Barghest. He kidnapped the now-cursed Silver Knight and imprisoned him in his castle. The Silver Knight would die unless Arthur surrendered his crown.

But at the advice of the Deathless Druid's ghost Tarna took up the Silver Knight's sword and armor and rode to his aid. Tarna took on the Barghest in battle but is unhorsed when a loose stone turned under her charger's hoof. But when the Silver Knight saw his beloved he gained new strength, grabbed Black Barton and leaped into the moat, threatening to drown him unless he turned the Barghest back into Sir Giles. Tarna defeated Sir Giles and forced him to remove the curse from the Silver Knight, after which he was killed by the Knights of the Round Table. But Black Barton was still alive and crawled up from the moat.

Golden Age Appearances
Wonder Comics #20