Claimed By the Demon Hunter 3 by Harley James

Fire Guardian Spencer Jameson has walked the earth for 400 years too long.
A proper English rogue with a list of bad deeds long enough to impress Satan.
His days of saving humanity were done, until Sydney came along…
The sassy mechanic with enough spunk to put him in his place.
When Satan’s son uses her family in a bid to unleash hell on earth,
She has no choice but to trust the smooth-talking scoundrel.
Unspeakable evil is near.
Armageddon, a heartbeat away.
They need to set aside their uncontrollable attraction to save humanity,
But it’s a test that could make the world burn to ash around them.
Settle in and buckle up. This ride is about to get bumpy.