Vampire Dragons are members of the undead. They sustain themselves by drinking the blood of others. It is said that they are only “alive” at night, and seem dead or asleep during the day, as they cannot endure sunlight for long periods of time. Vampire Dragons can only reproduce by changing the eggs of other dragons, puncturing the shell with their fangs and injecting venom that kills the baby inside.

Dragons are highly-intelligent reptilian creatures that—from a human perspective, at least—appear to live forever. Many different varieties of dragon exist, each with their own unique qualities, habitats, and behavior. Adolescence in dragons is usually marked by the growth of a hatchling’s wings, although not all breeds of dragons grow wings and some breeds have other traits that indicate the beginning of maturation. In Galsreim, dragons and humans coexist peacefully.

Sasori is one of the ill-Heart Dragons of Natasha's Cave. Out of them all, he is probably the most boring one. He sleeps soundly for every moment the sun shows its rays, and even when he's up at night, the only thing he does is hunt once and then guard the newer Vampire eggs and hatchies... or, more likely, sleep in front of them: being intimidating enough as a Vampire Dragon, he seldom feels the need to stay awake during guard duty.

Other ill-Hearts (such as Deidara) would tease him in saying that he didn't get bit with enough venom, and therefore he isn't nocturnal or diurnal. Sasori ill-Heart just shrugs off these comments and gets back to whatever he's doing. He does, however, have random nights where he leaves the cave completely for days at a time, before coming back with a smile on his face.