Doorways

The nephilim, born from a forbidden union between fallen angels and human women, were an abomination to God. They were gigantic, immensely strong, and very warlike.
Nephilim is a trilogy and is a story of redemption. In book one, the last and most powerful of all the nephilim is released from a prison where it was held for five thousand years. One remaining fallen angel has repented of his sins and now must face this giant in a weakened state before he can be brought back into God's presence. Before, he had other repentant fallen angels to stand with him. Now he only has three humans chosen by God to fight at his side.
A weapon created by angelic hands to destroy the nephilim can also be used to open doorways into other worlds, which would release onto earth terrible creatures from dark and violent ecosystems. The nephilim pursues the weapon in order to open a doorway into hell and release Satan as a physical being. The giant leaves death and destruction in its path, while one of the human warriors, a despairing widower who finds love again, fights to protect the ones he loves from the swarm of released creatures.