This is my favorite book in the Magic of Ethshar series,closely followed by The Blood of a Dragon. I recorded most of them, including this one, in 50-55 minute installments for my local Golden Hours radio service for blind or reading-impaired listeners. I also made CD copies for myself.
Valder is an Ethsharitic Scout who has been cut off by a Northern Alliance offnsive, trapped behind enemy lines, and is pursued by an enemy patrol which includes at least one wizard and possibly a shatra, a demon warrior which is more than a match for any single swordsman. He comes upon a hermit living in a swamp and the enemy patrol destroys the hermit's hut and most of his supplies, but the hermit turns out to have powerful magic of his own and is able to protect them, but this still leaves Valder alone, miles behind enemy lines, and with only his sword and sling to defend himself with.
In order to get rid of him, the hermit wizard uses what few supplies he has left to cast an enchantment over Valder's sword, telling him only its name, Wirikidor, and to not unsheath the sword until he has departed the swamp, nothing more.
It is left for Valder to discover the nature of the enchantment on Wirikidor -- a blade at once cursed and enchanted, a misenchanted blade that makes him unbeatable.
He learns that once drawn, Wirikidor can't be sheathed until it his drawn blood. In fact not merely drawn blood, but KILLED, and that it will always kill the first opponent it faces, and will not settle for wounding or incapacitating its "victim." On the other hand, Valder learns that it can then be sheathed, recharging itself to kill the next time it is drawn.
Wirikidor is not compelled to kill women or beasts, but it does enhance Valder's swordsmanship enough for him to fend off a young dragon long enough to escape up a tree. Then he learns that Wirikidor is even powerful enough to defeat a shatra in single combat, once it has drawn demon's blood.
This unprecedented feat brings Valder safely back through Ethsaritic lines, and to the attention of the Wizarding authorities, who take Wirikidor away from Valder to examine its properties, that is until one of the other charms on it compells its return to Valder by the quickest means possible.
Once the wizards have finally completed their investigation they give Valder the bad news:
[Warning Spoiler Alert - Read the book for yourself to learn Wirikidor's secret - or proceed at your own cost.]
1) Wirikidor means man-killer or warrior killer and it will always kill the first man or man-like person it encounters once it is drawn, and cannot be sheathed until it has killed.
2) Wirikidor is bound to Valder by a spell of true-ownership, which will compell its return to him by any means possible, even using earthquakes, tidal waves, or tornados if necessary to return itself to him. The true-ownership spell will also protect Valder himself from dying, but not from being harmed, unfortunately.
3) Wirikidor's blade has a spell which will keep it ever-sharp, and protect it from being damaged by anything short of a major catastrophic spell, a spell that would likely kill the wizard who casts it, along with anybody else within several hundred yards of Wirikidor.
4) The above spell of true-ownership has been corrupted somehow, and will only last until Valder has drawn Wirikidor approximately 100 times, plus or minus one or two, which means that after Valder has used the sword's power to kill 98 to 102 times, he will then be the only person in the entire world UNABLE to draw Wirikidor, and the first person who does draw the sword will immediately kill Valder with it and thereby become its master (or its slave) until it has claimed one fewer victims for its new owner.
5) This chain of circumstances will continue until 98 (or 102) of the sword's owners have died on Wirikidor's blade along with approximately 5100 other victims of its enchantment, and the sword's final owner is forced to turn Wirikidor on himself.
What aghastly spell!
The rest of the story involves Valder's use of Wirikidor to conduct clandestine assassinations of the Northern Alliance's top wizards and generals, until that is Valder realizes he has lost count of Wirikidor's victims and that he is in any case too close to the sword's magic number for comfort.
He decides to go into retirement, becomes an innkeeper, and discovers the last of Wirikidor's unfortunate curses: while he cannot die as long he owns Wirikdior, he does age, and undergo the usually bodily deteriorations of aging, and Valder doesn't care for the implications of that one bit!
Most of the story revolves around the various ethical dilemmas posed by ownership of "The Missenchanted Sword," and how Valder resolves each one in turn, and how he ultimately acheives contentment and happiness, which is not always true for a Lawrence Watt-Evans hero.
Finally, Valder learns how the spell became corrupted, from the wizard who cast the spell in the first place.