Well, I hope this help tried to keep spoiler tag and still provide some need info
Chris starts of being able to exorcise any demon he is hands on type of guy when the priest fail they call him.
Back story last family when he was young ( 8 i'd have to look it for specifics) to crazy man ( latter reveal was hellborn hunting him).
at 12 he goes in to haunted house and exorcise his first house on instinct.
Grandfather ex Solider(Spec Ops)/Farmer. after his first demon is banish he father starts calling in all the favors to train Chris
Has trained many forms of martial arts no belts just learning how to survive.
Trained tracker grow up helping search and rescue at the adirondack Mountains near Grandpa farm.
Gun training: An ex ranger he also called in all the favor he could to help train Chris after he saved his family from house demon
at the start of the series he just finished his probation period for NYPD so he has also been throu the police academy
Where most people have a scale of 10 for demonic activity,
He has two types:
house bound: the spooky has that throws stuff at you and drives you batcrazy.
Hellborn/Demonridden basic this is when the Human is kicked out and the demon has full control.
Demons thrive on sorrow, disappear and pain so they usually take over people that are down in dumps.
That story you hear about the crazy guy who came home killed his family thats usually hellborn in this series.
For hell born he uses grappling skills to hold them in place why rips the rider out and banish it (call God Hawk "Kirby" to take the entity to hell).
After he saves Tatiana things...got crazy..
She is they only born vampire ...as in vampires are made not born...expect her.
he saves her from a hellborn, she is greatly damage from sliver spikes she bits him as she need blood to heal and he is available.
After removing the spikes from her she comes to and stops drink. realize he is about to pass out from blood lose. She give him drop of her blood.
and he goes from badass exorcist to predator of predator .
so lot of stuff happen after this
Tatiana speak (she has not spoken sense she was 8). which is big deal and she start imporving
he become tatiana Mate.
he is a self fallen angel on mission from God (lots of spoilers their)
Tatiana is his soul mate (self fallen angel as well).
God's chosen warrior put implace not to wipe out demons so much as keep them in check as they are apart of the human condition
badass exorcist to predator of predator .
is basically immortal
extreme healing ,
can use his aura to do stuff that makes witches piss them self because what he does should take 10 to 20 of at least one coven working together.
He scares all the old vampires because he basically a 2 year by their reckoning yet he can hold his own with 200 year old vampire ....on a normal day...unless Grim driving thats when his skills go of the charts
Grim is his fighting persona that comes out in book 2 basically a savant a fighting and surviving slight anger problem is comes with this.
Can make mone edge with his aura (blade the sharp enough to cut at the molecule level).
Has WereBear-Wolf that always near by ( Wolf dad was Fenir and a kodak bear wsa the mother, may be the reincarnated soul of Great Bear form Indian Folklore)
Tatiana Demidova
Queen of the Vampire
basically immortal
extreme healing ,
only 24 at the start of the series very advanced.
Bonded with Chris as she has Chosen him for her mate.
She is very powerful both as a fighter, it took 3 elders (1000 old to keep here in check when she went crazy on night trying to get Chris because he was in danger
And as business Woman she leads the New York Coven and over the the stock market, the Covens connection and wealth is astounding and she continues to leverage it and out shine others.
Her voice has power , she can give her word power that force people obey, or make a note so clear that it can punch a hole throw solid steel.
When Chris/Grim(short for the Nickname of his prosona : Grim Reaper) and Tatiana fight they fight as one and their minds and being open to each other greatly . they always know were each other are but when they fight this knowledge goes for level 1 to level 10 and they become truly one fighting machine.
They both can be killed it just really hard.
also Tatiana is allergic to sliver while Chris seems to be allergic to DU(Depleted uranium)
the US army is also unsure what to do about chris as he is to powerfull,
He has been attacked few time by a rogue Black ops group......well he has responded with extreme measure speciality when they tried to kidnap his God Daughter.......lots of death happened.