Gantz Room -- A lot of spoilers

The beings we humans call vampires are enemies of Gantz just as the various aliens we have seen are. Contrary to what we've been lead to believe they do not fear the sunlight nor crosses hell one of them was wearing one.They first make their appearance at the end of the Dino Mission as the Gantzers begin returning to the apartment. Without warning they attck killing the people who don't have a suit and then try to kill Izumi who they seem to reconize from somewhere before. He escapes and they turn their attention to the Old Man but he makes it out of there as well.

Here is the little info we know about them since there hasn't been a actual mission to hunt them down but we are led to believe that past Gantz teams have been sent out to fight & kill them. Vampires were once human but under went their transformation due to nanomachines which were discovered several hundred years ago. These little microscopic machines are like a virus, they enter a living creature and then alter it's cells, giving the person new powers and abilities. All vampires have Eczema rashes on their backs in the shape of bat wings and they suffer from headaches from time to time. They like to drink human blood and see humans as their natural prey, so killing people without remorse or mercy comes as easy as breathing. Some of the abilities they have rival that of the Gantz suit. They are as just as strong in terms of strength to the Gantzers, almost as fast in terms of speed, and can even jump pretty dam high or a distance. Also physically they can heal minor wounds instantaniously and their bodies can take a fairly good beating. One was hit by car and was unharmed. What's really amazing is that they can create things out of thin air from their hands mostly weapons, probably thanks to the nanomachines. Like handguns and swords. But these weapons are useless if the person is wearing a functioning suit, one vamps sword broke after it struck Izumi and most likely bullets would bounce off.

For some reason they don't know that much about Gantz as you would think. Since their being hunted by Gantz they consider him their sworn enemy, calling his people vampire hunters. They know the powers of the suit and the weak points to disable it. Invented special contact lenses and sunglasses to see Gantzers when they cloak. And that the people in black suits are under the orders of the Giant Black Ball. But that's about it. They don't know why they are being targeted, who the people in the suits are, how they're chosen, or where they come from. Hell they don't even know how dangerous the X-Gun is at first until they see it first hand at the end of the dino mission or no one who has seen it lived to tell about it. For this very reason they try to collect as much intelligence as possible. Taking pictures with camera phones, even trying to capture Izumi for questioning.

They're pretty smart in that sense having regular meetings, organizing together to fight in a all out war, learing and planning as much as possible to counter the Gantz threat. Hell they even know about the Oni Aliens who they have a mutual understanding with that the hunters as they call them are the enemy. But they have one major flaw a superiority complex that leads them to believe that they are stronger and that can easily defeat Gantz. Which time after time, their under estimating their enemey has proven fatal. Hell we've seen more vampires killed by Gantzs then the vamps killing his team back. Luckily they aren't that strong I would say at least equal to our ill fated heros, they die like ordinary humans so all you need to do is explode their ass with a X-Gun or slice and dice them with a Gantz Sword.

Kurono Akira - This is Kurono Kei's little brother he is a vampire apparently turned into one recently. Akira has a whole chapter dedicated to him where he goes to a vampire conference to where he was invited. They talk about the nanomachines, also about the symptons that they suffer from (He has all them), and about their greatest enemy the Gantzers. At the end of the conference he is stopped by 3 other vamps who slice up four of his classmates into pieces and feed their blood to him as a initiation gift.