Location: northwest of Skingrad (link goes to the Daedric Shrines Map at UESP Wiki)
Minimum Level: 10
Offering: Bonemeal or Ectoplasm
Reward: Ring of Khajiiti
Objective: get rid of the Necromancers (yeah, those guys) at Howling Cave
Probably the hardest part of this missions is finding the shrine in the first place. I don't remember anyone putting a marker on the map for it. When I've found it, it was because I was running around in the wilderness between Kvatch and Skingrad and saw the shrine icon on my compass. It's more or less between the Shardrock Farm and Cursed Mine, kind of west-northwest from Skingrad's western gate.
Basil Ernarde will tell you that Meridia hates undead, so undead remains would be a suitable offering.The Prima Guide says that there is some Ectoplasm under a nearby bush, but I've never found it. But Bonemeal and Ectoplasm are both pretty easy to find by the time you reach the appropriate level to activate the quest.
So off you go to Howling Cave. Take the northern passageway, go through the secret door at the end and deal with the five Necromancers and their undead minions. When the last Necromancer is dead, you'll get a message telling you to go back to the shrine to collect your reward. Oh, and if you have any wild ideas about clearing out the Necromancers first and then activating the quest later, forget it.
Being a sneaky-type, I consider the Ring of Khajiiti to be a must-have artifact. While the Speed bonus is nice, the Chameleon effect is nicer.