Necromantic drakes are intrinsically linked to the Negative Energy Plane, and become more and more knowledgeable about death and undeath with age. Such knowledge isn’t especially healthy, and as the drake ages, its body bloats and swells with Negative energy. This either kills the drake or seamlessly it becomes another undead monster.

Lest adventurers close in to avoid magic and breath weapons, they’re in for a nasty surprise; necromantic drakes impale foes on their many spines, and just residual energy from being nearby animates the skeletons to attack any adjacent enemy.