The Abyssal Forge Hammer was a powerful weapon that originally belonged to the Mad Smith and was used in the construction of the Abyssal Forge. It later came into the possession of Death at the end of his quest in the Shadow Lands.
Damage (Slow) :
Complete the Abyssal Forge DLC. This weapon scales with Death's level, so from level 20 this hammer can reach level 30, becoming stronger in each aspects. In the Deathinitive Edition, the progression to level 30 is possible in NG+ only; instead in NG, the hammer isn't improvable.
|“|| The Mad Smith built this hammer to aid in the construction of the Abyssal Forge. Imbued with a dark energy, the hammer can shatter even the thickest armor and set all it touches ablaze.|
— In-Game Description