Hades features an item called Daedalus Hammer. On this page you will find basic information about it, you will find out what it is for and how to use it.
The Daedalus Hammer is an artifact that can be used to upgrade your weapon. You'll get it as a reward for cleaning the room, or you'll buy it from Charon.
During one game you can only get two Daedalus Hammers, but their effects will stack.
One Hammer will be in Tartar or Asphodel, and the other one far later on in Elysium.
Hammer improvements depend on the weapon you wield. Some of them are small improvements and some completely change the way you play. It is worth remembering, that improvements affect the Attack or Specialty of a given weapon.