The Elemental Detective's World

 Science rules this world, more than religion but some 'religious' fears are still strong. Mainly that anything smacking of 'witchcraft' still genders fear of the unknown. If science can't explain it the people fear it.

When the vampires, shifters, and immortals introduced themselves they brought with them new sciences including DNA and medical advancements. Of course it was mainly to explain themselves to the masses. They didn't want to be hunted or misunderstood. Legends had already maligned them and they were tired of hiding.

Vampires had a virus that was a mutation of rabies. It also had RNA strands that halted aging and sped up healing using blood as energy source. 

Shifters had mutated RNA strands which were linked to animal DNA. They aged normally, but they too had sped up healing. It was also inherent in their DNA so they could pass it on to their children.  

Immortals had mutated DNA which stopped the aging process at the person's peak age and sped up their healing processes. 

This is how they explained themselves. They were not demons or devils or evil creatures, no more than mundane humans themselves were.

Charters were made with the Others to have a common law and each city had its own special Charters with the Other communities. Special divisions in the police forces were created to enforce those Charters.

As the Others settled in more of their past became known and humans learned of the Elementals, beings that could control the elements.  Vampires painted them as evil creatures. But the shifters and immortals explained that the Elementals were the ones that united the Others, made the Universal Laws, and set up the Masquerade, curving both the vampires and shifters blood-thirstiness and arrogance. All of the immortals and most of the shifters realized it needed to be done, but a lot of the vampires did not like being told they couldn't do as they pleased.

Humans were ambivalent about Elementals, especially since the shifters and immortals said that they had faded away over the centuries. Though they thought it more to do with the vampires hunting them than anything else. Elementals could still be around, just doing their own version of the Masquerade.