Rufo said: One would think trying to force your penis into a vampires mouth would be a terrible idea.
Then again, drinking blood from one's cock is quite advisable, more so when it's erect since it's practically a blood-filled pneumatic cavity. The problem is how to stop the blood after you're done, but if you intend to kill the prey afterwards it won't matter. Well, there's also that concern about STDs, but if you don't break the blood-duct barrier (i.e. bite the balls) you'll mostly be safe.
KazuyaRazuKazama said: ^Touhou on Danbooru: Cause even on pics showing a loli vampire girl having a giant cock shoved in her mouth, you can STILL learn something.
It would be a hydraulic cavity (pneumatic being air from L. pneuma meaning "wind" or "breath"), or maybe sanguinary would be more apposite.
Unless you have one of those ED implants that has a pump and an air bladder! That's an actual thing. I got bored and read a pamphlet about it while waiting around in my urologist's office one time.