The Black Heterodyne/Mad

The Black Heterodyne
Little is known about the Black Heterodyne except that he was a very early member of the House Heterodyne, and that his tomb has a caution against opening it. This may fall in line with the rumor of an undead Heterodyne. More evidence comes to light when the Castle tells the of the "miraculous" waters of the spring called Dyne, from which the Dyne River was "coaxed" by Egregious Heterodyne, to the destruction of the first Heterodyne castle. A very dark-haired member of the original raiding party drank the waters despite the warning of the local priestesses, who told him it would be result in a horrible, insane, death. (Or occasionally miraculous healing.) We know he liked it, and that it made his teeth grow instantly. Later, as a river, it even grew long pointed teeth on ducks.

It seems reasonable (if any of this can be so-called) that this Heterodyne could both be called "Black" (by temperment and hair color) and have been rendered almost invincible/immortal. Not a tomb one would want opened!