Hircine (Quest)

Hircine's followers have told the Hero that, in order to summon the Daedra, they must leave an offering of a wolf or bear pelt at the statue.

Walkthrough
Hircine will ask the Hero to travel to Harcane Grove in the southwest, to kill a unicorn and bring back its horn. The unicorn is guarded by three special Minotaurs, and the unicorn itself may also be hostile.

Return the horn to Hircine, who rewards the Hero with the Savior's Hide, one of the best suits of light armor in the game, with a constant 25% Spell Resistance.

Method one
Enchanted or silver weapons are needed to kill the unicorn. One strategy is to jump up on something and shoot it with silver arrows, then finish it off with a sword or dagger.

Method two
Another method would be to mount the Unicorn (by avoiding the Minotaurs completely and approaching it without a weapon drawn), and leading it to fight difficult monsters. Despite its strength, it's just like any other horse in the game, in that it has a slow overall attack speed and a high knockback rate (low agility). Lead it into a confrontation wit a quick, difficult creature (Clannfear, Mountain Lions, sometimes the quick attacks of a Black or Brown Bear will finish it), and finish off the creatures (or grab the unicorn horn and run) once the Unicorn is dead.

Method three
A third method is to mount the unicorn and travel to a high cliff. Jump off the cliff (which is not too high) while riding the unicorn and it will suffer fall damage; repeat until the unicorn has died.

Method four
Another Method is to use a destruction staff (e.g. Staff of Shock) and electrocute the Unicorn and Minotaurs. It is also good to have Shadowmere (rewarded after a Dark Brotherhood quest) as he can attract some of the attention (he attacks enemies which makes him useful and is quite fast).

Trivia

 * One easy way to have the unicorn killed is to take it into Cloud Ruler Temple, close the gates, and let it watch the two blades fight. This causes it to attack and the blades will kill it.