The Coldest Sleep
Like the "Broken Vows" mission, this is a straightforward hit. Havilstein Hoar-Blood is a Nord that killed a chieftain back in Solstheim. Hoar-Blood lives on Gnoll Mountain, which is east of Bruma. The Prima Guide tells you that Hoar-Blood is five levels higher than you. It's off by a factor of four: Hoar-Blood is 20 levels higher than you and especially skilled in Blade, Marksman, Sneak, Light Armor and Security (sound familiar? Yep - he's an Assassin).
I've always had the best luck with this mission by approaching Gnoll Mountain from the east. This means that Hoar-Blood and his pet wolf (a bit stronger than your average Timber Wolf) have to charge up a steep slope to get to me. Even though his Acrobatics skill is up there, I've managed to get him stuck on that slope and the nearby rocks to the point where I was able to make a pincushion out of him while he could only hurl obscenities. Oh, yeah. Life is good at moments like that.
Your payment and orders are in Nornal, an Ayleid ruin southwest of Cheydinhal (not southeast as the Prima Guide tells you). It's actually closest to Arkved's Tower, where you would have gone for Vaermina's Daedric quest. Aside from that, it's not close to any quest locations, although you might have gone there for a Grand Soul Gem in the "Cure for Vampirism" quest (it's one of several possible places to get one). Otherwise, you'll have to hoof it. And unlike your previous dead drops, this one is actually inside the ruin, but not terribly far in. Just follow the entrance corridor to where it tees and go right. You're going to have to go underwater, pick the lock on the gate and you'll see the chest right in front of you.
If you're interested in exploring, Nornal is a four-level Marauder lair.