Hades

Hades was a Greek Immortal who supposedly ruled the underworld. (PROSE: Katarina in the Underworld) He used the aliases Hadley and Colonel Nicolevic during the 20th century. (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)