Battle to the Death

Liches weren't something that existed naturally.

This meant that no one was born a lich, and that it could only be formed if a mortal signed a contract with a demon.

The people who were prone to being tempted to become a lich were often those who were desperate to live— after all, liches could live as long as the demon they're contracted to was alive.

Moreover, some were not willing to give up in their pursuit of power.

They would then sign a demonic contract, giving up their lives in exchange for eternal life and power.

This included mages and warriors that were close to death, which were also the favorite target of demons since they would be able to gain a loyal subordinate just by sharing some of their demonic power.

Divine power is an energy of higher beings.