Hellmaster's Jar (Japanese: 冥王の壷 Romaji: meiō no tsubo; lit. "jar of the king of darkness") is a type of magical vase appearing in Slayers EVOLUTION-R. The vase's purpose was the manipulation of souls: a Hellmaster's Jar could be used to move a soul from one body to another, or to provide refuge from death for a disembodied soul.
Most (if not all) of the jars were created by Rezo the Red Priest. After Rezo-Shabranigdu's destruction at the hands of Lina Inverse, Rezo's soul -- and the piece of Shabranigdu within it -- was preserved within the jar. The jar was protected by Rezo's servant Ozel until Rezo's soul could be transferred into the body of Posel Korba Taforashia, resurrecting him.
Another jar was used to bind Posel's soul into the form of a stuffed toy, and yet another vase was found in an unnamed ruin by Lina and the others which kept the soul of Naga the Serpent in a suit of armor.
The jar's connection to Hellmaster Fibrizo is unknown, possibly only named after him because of the mazoku lord's ability to manipulate the souls of the dead.