Demon Summoning

You'll receive an enchanted dagger, made out of dragon bones and forged with hell-fire, giving it demonic properties. When killing someone with this dagger, you'll summon a Demon to take over its body and become your servant, viewing you as its master and follow your commands. While they vary in appearance, size and intelligence, all demons possess superior strength, speed, resilience and senses to that of humans. As for common powers that demons possess there's flight (Either through wings or levitation), fire manipulation and poison generation. All demons are reborn in Hell when killed, but depending on their power, this can take a few years or centuries. The only known way to kill a demon (And other spiritual beings), is to eradicate their ''essence'' (For demons, this is achieved by large amounts of ''Sacred Energy''), which makes it stop existing as an individual being, returning it to the universe as the prime material that makes it up.

Going back to the dagger, you can store within a personal pocket space when not using and if broken, the demons made by it shall still obey you, but you'll need to forge a new dagger to keep creating demons. When in a dire situation, you can use the dagger on yourself and transform into a powerful demon. In exchange of that power, you'll become unnable to use the dagger, as only humans can wield its true power.

How will you use this dagger? Will you destroy it? Or perhaps raise your own demon army?

PS: This was based on the Forgemasters from Castlevania, as I recently rewatched the Netflix show. In this setting, demons are divided into Natural Demons and Converted Demons, with the first ones having been born in Hell (Or banished there during the Celestial War eons ago) and the others were damned souls, which eventually became demons after centuries of torment.