Garamon, from Ultima Underworld
Garamon is a mighty and very dead wizard. He is the main ally of the Avatar in Ultima Underworld I.
Garamon and his brother Tyball were mighty wizards, so powerful that they lived in the extremely dangerous 7th and 8th level of the failed colony in the Abyss. One day, they did a mistake and accidentally summoned the Slasher of Veils. While they tried to find a way to banish him, Tyball was seduced by the daemon and killed his brother in cold blood, hiding his bones in the lowest level.
But even dead, Garamon was mighty. He managed to summon the Avatar to help stop his brother, and gave the Avatar hints while in sleep from time to time. But only after his bones were buried could he give concrete help, telling the Avatar how to banish the Slasher of Veils. While the Avatar did so, Garamon rescued the people of the Abyss. He finally told the Avatar goodbye on Earth, before escaping to the Void, finally at peace.