Dracolich

Even as long-lived as they are, all dragons must eventually die. This thought doesn't sit well with many dragons, some of which allow themselves to be transformed by necromantic energy and ancient rituals into powerful undead Dracoliches.
A Dracolich retains its shape and size upon transforming, its skin and scales drawing tight to its bones or sloughing away to leave a skeletal form behind. Its eyes appear as glowing points of light floating in shadowy sockets, hinting at the malevolence of its undead mind.
Though the precise ritual required to create a Dracolich is unknown, the fact that this creature is a lich implies the presence of a Phylactery of some sort...