Anybody have theories on who the bat possibly is? My personal theory is that the bat is Sandiago the alchemist/ nomad in mirage. He just looked evil, from his eyes to his dark clothing. Also, if you look at the Mirage teaser of them showing some of the main characters we meet in the world, you'll see how he's more over to the right, closer to the antagonists ike xerxes and the mirage mobs then the actual good guys.
All we know about the Bat at the moment is that they're a child of spider, a brilliant shapeshifting Vampire, a master of illusion and subterfuge, and with a heart as black as night. I don't think we will have seen them in-game yet, but that we will do in the next world. Although they could well be someone in one of the organisations we trust, like Ravenwood or the Arcanum. I'd actually like for the plot twist in the Bat's story to be that they've infiltrated the Cabal and wish to stop them, putting them on our side, unlike the other children of Spider. But, of course, they're likely just going to be an ally-turned-villain, because of the heavy emphasis on their ability to hide. Of all the allies currently in-game to pick from, I'd say the obvious choice is Velma von Venkman, but I think that should only be used if the Bat turns out to be on our side. We don't know very many people that strike me as shapeshifting Vampires to be perfectly honest. If Empyrea is the next world, and involves Bat, then it could well be someone from Wysteria as that's the only place we currently know has access to Empyrea, and Belladonna Crisp always struck me as a vampire in a human form. The way she speaks, the way she acts, she just gives off that feel to me. It's definitely an unlikely plot twist, but that makes it even better.