The Child of Darkness

A story about the collaboration of Avenger, S.H.I.E.L.D and Hellsing organization.
Its a story of humans who want to be more powerful and tried to play the game of gods.
They create things that can doomed the entire world.
An unending desire to be on top.

This is where 2 different species that they thought was a myth decided to join the team.

While God created adam and eve, Satan tried to copy it and created a perfect curse which is
Her. Achlys the first and last creation of Satan but punished by God to live with a lifelong contract and crave of blood. Basically similar needs of a vampire.