Location: way east-southeast of Cheydinhal (link goes to the Daedric Shrines map at UESP)
Minimum Level: 20
Offering: Daedra Heart
Reward: Goldbrand (longsword that does 22 points of fire damage)
Objective: complete the "Tournament of Ten Bloods".
This is a series of one-on-one matches between you and opponents from the nine other player races. Once you enter Boethia's portal to Oblivion, you cannot stop to rest and you cannot return to Tamriel until the last one is dead. Stock up on potions, spells and soul gems to recharge your items before you go. Be careful of the bridges over the lava. It's not hard to get pushed over the edge by a good whack or two. Getting dumped into the lava is usually a "bad thing" unless you're the one doing the dumping.
Considering that you can make an enchanted weapon with better damage with Sigil Stones or on your own at the Arcane Univesity, I think I'd take a pass on this one unless you're just bound and determined to collect all of the Daedric Artifacts.