"YOU'VE COME BACK AFTER A THOUSAND YEARS TO FINISH THE JOB!"
The swordsman looked at his partner to the left. "Is that a talking skull?"
"OH PLEASE DON'T! I'M HAPPY WITH MY EXISTENCE! HAPPY!"
Parietal is a human skull of generally normal size and shape. The surface is aged, devoid of all flesh, and slightly gnawed on by various vermin. Parietal has a large wound where the parietal bones of the skull are located- the primary reason for his name. The wound varies depending on the criteria below.
Being the former human's spirit housed in the skull, Parietal's eyes glow when he speaks, and the illumination is comparable to a torch, albeit of different colors ranging from red, blue and purple. Parietal speaks in a disembodied voice that listeners can determine come from the skull.
Caught in a ferocious battle, Parietal's unlife began when he suffered mortal wounds at the hands of someone wielding a historical artifact. Most prominently was the blow he received to the parietal bone of his skull, which caused his death. Parietal eventually gained awareness and control over his new state of existence, unable to leave the battlefield where he fell.
Parietal's memories of his life before the battle that ended his life slowly faded away. He fears the weapon that killed him, immediately recognizing it and whoever wields it as his master. Parietal falls into hysterics easily, courts melodrama whenever possible, and cannot conceive that his master does not actually want to kill him. Parietal is a constant nihilist, defeatist, and is prone to immediately proclaiming doom or impending catastrophe.
Parietal maintains his knowledge of history as of the time of his death, and any skills he may have had in his former life, albeit without the physical capability to utilize them.
Parietal is the last remnant of an evil tyrant whose death at the hands of a hero long forgotten allowed a greater evil to enter the world- and Parietal's past knowledge is the key to closing said portal, doorway to the void, or sending the evil back to whence it came. If players can convince the skull that they're not going to die.
Parietal's death was the sole evil use of a good artifact, and until that wrong is made right, the artifact is powerless.
Should a speaking/intelligent weapon be the cause of Parietal's death, they should constantly bicker as the weapon threatens the cynical skull.
"Oh, my god. We're dead. We are so dead. Dead. Dead. Dead. And it's your fault!"
"I'm a sword! I can't help it if a past owner decided you smelled bad!"
"I can't believe the monster that's going to kill me a second time is talking about how I smell!"
"I'm not going to kill you a second time!"
"DEAR HEAVENS SAVE ME! MURDERER LOOSE! DON'T LET HIM KILL ME!