Kalula is basically just an experimental Lugia. Or perhaps she's a Lugia that got sucked through a wormhole and spit out into Bloodborne or Dark Souls? Or maybe she's just a hot goth mommy Lugia. Her origins are largely a mystery, which is a fancy way of saying the writer hasn't thought that far back yet, but what isn't a mystery is that she is quite unique. Her chains for example, appear to be more than just mere acessories... They move and flow with her mannerisms and Kalula has been seen controlling them directly to snatch up unsuspecting cuties, or bind her opponents. Despite her rather scary demeanor and the fact that she is prone to devouring someone at will without a second thought, she was mostly a good girl. Very warm and welcoming, extremely friendly...maybe too friendly at times...getting hugged by a gargantuan behemoth can be rough after all.
As far as general powers go, well she is a pokemon. She doesn't appear limited to only knowing four moves, but rarely uses any at all. She has been seen using Future Sight, Hydro Pump, and Rain dance, as well as Recover..but she can also Fly, and seemingly control her chains with her psychic abilities, and has been seen surfing through the ocean.
Kalula also has a Veil over her eyes. It's been theorized that she see's the world through a psychic eye of sorts, since her veil is completely solid and cannot be seen through. No one knows what the purpose of the veil is, or what she look like underneath as the Veil seems to be held on tightly by a strong pyschic force, any attempts to remove it have been unsucessful..and met with a swift trip to her stomach.