Miasma

' Miasma is a weapon found behind a locked door in the Dungeon's basement. You need the Crow Emblem Key to access the door leading to Miasma, which is dropped by the Crow Mauler. Defeat the Crow Mauler as a test of your might and skill in the game, and the player is rewarded with the mighty Miasma. However, you can break the door open, sacrificing your weapon. To do so, attack it until you don't stop the fight after the first hit. This way you can get miasma early on.

Description
"An otherwordly sword that oozes toxic gasses. The sword is said to house the strength of 6 men."

Stats

 * +92 Attack, 10% Bleeding

Trivia

 * The weapon is most likely inspired or a direct reference to the weapon, Soul Edge. Both have the same design (both are single edged swords with an eye near the guard of the blade), both have bloodthirsty tendencies, both thrive in chaos, pain, and misery of the world, and both are cursed weapons. Unlike Soul Edge though, Miasma does not seem to act as a parasite and does not overpower or take over its wielder.

Quotes
Miasma is a legendary sentient sword which will communicate to the player by making them hear a voice in their head.
 * "Come and find me. Let the blood flow." (Upon interacting with a heavy iron door)
 * "You miserable mortal worm,"
 * "You wish to use me?"
 * "Chaos, pain and misery."
 * "Those are the reasons I was created."