Banesteel Longsword

The metallic green alloy of this blade was forged in the bowels of Avernus, and still carries the unbridled fury of the fiery plane. This hardened and hate-filled blade gives the following effects:

• You gain a +1 bonus to all attack and damage bonuses when attacking a Celestial or Fiend with this weapon. Whenever you deal damage to a Celestial or Fiend with this weapon, their hit point maximum is reduced by 1 until the creature receives magical healing. 
• When you hit with an attack roll using this sword, the target takes an extra die of damage (1d8 or 1d10, whichever applicable). This damage is fire damage.
• Whenever you are carrying this sword on your person, you are immune to effects that would cause you to be frightened or charmed by a Celestial or Fiend.
• This sword scores a critical hit on a roll of 19 or 20.
• This weapon has the finesse and light properties, and can be wielded by a creature with proficiency in shortswords or longswords. 
• Whenever you score a critical hit on a creature wearing adamantine or banesteel armor, the critical hit occurs regardless of the armor's effects. 

Curse. Whenever you are wielding this sword, you are filled with the rage innate to its home plane, which can cause you to lose focus. You gain disadvantage on Constitution Saving Throws required to maintain your concentration on a spell while you have this sword drawn. 

Proficiency with a Longsword allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Damage: Fire, Versatile, Sap