Hermaeus Mora

The Mora quest is the last Daedric shrine quest, and can only be completed if you've completed all the rest. You'll also need to be level 21 or higher, and have reached the section of the main quest that requires a Daedric Artifact. If you've fulfilled these requirements, then go to sleep at a bedroll or a bed, and when you wake, Casta Flavus will be standing nearby, telling you that you've been summoned to the Shrine of Hermaeus Mora, high in the mountains in northwestern Cyrodiil.

Now, getting to the shrine is going to be a task in and of itself, due to its elevation. Before you head out, be sure to buy or steal a horse, as it'll cut down your travel time immensely. With one in hand, travel to Sancre Tor, just above the "y" in "County Chorrol" on your map. From there, head west or northwest until you start seeing sets of stone stairs cut into the mountain. Although you initially start out heading away from the shrine, you'll eventually wrap around to the northeast and cut back towards the shrine. With a horse, you'll be able to just outrun all of the enemies that stand in your way.

Mora's Task After getting to the shrine, speak to Mora to learn what he needs you to do. His task? You're to capture ten souls and place them into a special soul gem of his providing, using a special Soul Trap spell. You'll need to gain one soul of each of the sentient races of Oblivion, meaning one Nord, one Altmer, one Khajit, and so on and so forth.

Mora needs souls, and he's not particular about where they come from.

Obviously enough, this can be as hard or as easy as you want to make it. The hard way would be to track down bandit, marauder, necromancer, and conjurer caves and attempt to find all the souls that you need in that fashion. This'll work, but it'll take a while, since some races are poorly represented in these environments, such as Argonians.

Alternately, if you're not opposed to a bit of murder now and again, you can simply travel back to the various Daedric shrines that you've passed through earlier and kill the worshipers there. None of them have any further relevance to quests in the game, and they're far enough away from guards that you're unlikely to earn a bounty for their slaughter. Of course, if you're just looking to get some souls, no matter the cost, you should be able to find one of each type of race in most of the major cities....

Mora's Reward Mora doesn't particularly care where the souls he required come from, even if they happen to be Daedra worshipers. When you capture all ten, you'll get a note telling you to return to Hermaeus Mora, who hands over the Oghma Infinium, a special book covered in Daedric text. You can read it in one of three manners: Steel, Shadow, or Spirit. Each has its own suite of bonuses to your attributes and skills.

Path of Spirit: +10 to Destruction, Conjuration, Restoration, Intelligence.
Path of Steel: +10 to Blade, Heavy Armor, Blunt, Strength.
Path of Shadow: +10 to Sneak, Security, Light Armor, Agility.

Note that these bonuses can get you up over 100 points for both your skills and attributes. In the case of skills, this doesn't seem to have much of an effect (your Heavy Armor won't protect you any better at 110 than it does at 100, for instance), but it's a great way to permanently add another 10 points to a critical primary attribute if you've already maxed it out. We're not sure what happens if you add 10 points to an attribute that hasn't been maxed, but we're betting that you'll wind up hitting the same of 100 points when you eventually reach that number, instead of benefiting from the increased cap of 110. Note also that the bonuses to your major skills will cause you to level up instantly, possibly as many as three times.

And...that's it for the Daedric quests. There's nothing more to see here, but the rewards were hopefully worth it to you. Azura's Star and the Skeleton Key are certainly worth using throughout the game, with other items, like the Ring of Khajiiti, being tremendously useful in other situations.