Hades

Hades was an Immortal, known in Greek mythology as the ruler of the underworld. (PROSE: Katarina in the Underworld) In later centuries he lived among humanity as Niccolo Machiavelli, Cardinal Richelieu, and Maximilien Robespierre, and in the 20th century as Hadley and Colonel Nicolevic. (PROSE: Deadly Reunion)

Hades was approached by the First Doctor on Katarina's behalf. Hades refused to overrule his judges' verdict that Katarina was neither good nor evil. However, his wife, Persephone, convinced him that Katarina deserved to enter the Elysian Fields. (PROSE: Katarina in the Underworld)

When he tried to take over Earth during the 20th century, he was stopped by his brother Poseidon and forced to return to the Underworld. (PROSE: Deadly Reunion)

Appearance
When the First Doctor and Katarina met Hades in the Underworld, he appeared as a slight, bearded man with flowing auburn hair. He was naked apart from a length of white cloth tied around his waist, and carried a battered helmet that could make him invisible. When angered, he grew much taller, and was surrounded by a fiery aura. (PROSE: Katarina in the Underworld)