Tenebra Remanis
The Black Prince is a very prominent member of the Drakan family, and is a Vampyre Lord. He appears only once in the Return to Canifis novel and is yet to appear in game.
It is revealed that he was the one who sent Jerrod the werewolf over the River Salve to retrieve Gar'rth, and also sent the Wyrd, an unknown class of vampyre, most likely a vyrewatch, to weaken the holy barrier of the river in preparation for an impending invasion of Misthalin.
In Gar'rth's letter to Kara-Meir, it is revealed that The Black Prince is in fact Prince Tenebra, a prince of Misthalin that rode to war against Morytania centuries ago, and that he is Gar'rth's father. As vampirism is not inherited, and Tenebra was once human, this made Gar'rth Half Human, Half Werewolf, as opposed to Half Werewolf, Half Vampyre, which is why he was able to resist Zamorak for so long.
As a human, Tenebra was the eldest of The Five Princes of Misthalin who rode to war against the dark forces of Morytania centuries ago, where he was presumed dead after he went missing in battle. This would leave Gar'rth as the rightful heir to the throne of Misthalin, and with Gar'rth currently in his father's possession, Tenebra now plots to invade Misthalin, using several large siege machines built in the slums of Meiyerditch to take his place as Lord of both the Land of the Dead and of the Living.
He seems to have some form of rivalry with Vanescula Drakan.