Alucard ("Dracula" backwards) is from several sources of vampire fiction and Konami doesn't own the name. The image we use for him, maybe, but not the name or concept.
Genbu, Seiryu, Byakko and Suzaku are from Chinese creation myth and are certainly available to us. (Suzaku, the phoenix, technically already exists as a Rare in MArcomage, just not by that name.)
As long as we're naming things from anime and the like, Alastor as we use it is from
Shakugan no Shana and Order of the White Lotus from
Avatar the Last Airbender. As these are not starring/title characters/entities, I've always considered them homage rather than infringement. That doesn't mean that copyright holders would agree, however.