I got an idea and started sketching it out before double checking the rules. Whoops! They want a wondrous item, not a weapon. I decided to keep going, just for the practice. I used the Aztecs for inspiration. Its probably slightly underpowered given its creation cost, but a coup de grace attack is hard to figure. Technically true resurrection should work on the victims and if this were an official entry I'd have removed that, even though I think its dumb that true rez works on the soulless. As it stands now, this comes in at exactly 200 words.
I also used semi-colons. I like using semi-colons; they make me feel smart.
Enjoy it for your game!
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Sword of Xitecka-Telacop
In the jungles far from the known kingdoms lie the twin cities of Xitecka and Telacop. Banding together to resist foreign invaders, they have used the death magic of the Xiteckian priests and the craft of the Telacop masters to create swords for their warriors. The blades are created from magically empowered obsidian, identical in all but appearance to the best steel. They each have a handle of bone from a jaguar the warrior must have slain for himself before being considered worthy of a Sword of Xitecka-Telacop. Recent tradition encourages warriors to engrave a stylized pictogram on the handle celebrating every major victory achieved using the sword.
A Sword of Xitecka-Telacop allows the wielder to make a coup de grace attack as a standard action. Opponents that fail their Fortitude save and die must also make a Will save (DC 10 + damage dealt) or have their soul cleaved, preventing the victim from benefiting from the following spells: limited wish, raise dead, resurrection, reincarnation, speak with dead, or true resurrection; miracle and wish work normally.
Moderate necromancy; CL 7th; Craft Magic Arms and Armor, death knell, death ward, Price 22,315gp; Cost 11,157 5sp + 893 XP.