The more lifespan the Angel Devil takes and uses, the stronger and more deadly the weapon becomes, providing an incentive for humans to give up most all of their lives in more dire situations.

While the Angel Devil’s powers have yet to be fully fleshed out in the anime adaptation, they were explored in the manga, though if you don’t want to have them spoiled as the first season of ...

The Angel Devil has the ability to steal time from both allies and enemies, using said time to forge powerful weapons that become stronger based on the more years that are placed into them.