A downhill approach to Orphan’s Rock is incredibly risky, however, as the mountain is chock-full of fatal falls, and any such attempt would involve more time and save-retries than virtually anyone is willing to put up with- so instead get your toughest, most powerful follower, and head to Helgen, the closest fast-travel point to Orphan’s Rock.
From the ruined fortress of Helgen, you will want to start at the fast-travel point, the Southeastern gate. Head East along the cobble road that leads from the gate until you see a pile of stones- a marker plinth- on the left-hand side of the road. You will know the right one as there is another just upslope from it, and a third directly ahead if you pass between the first two. This is the path to Orphan Rock.
Approach cautiously- two robed spellcasters wait uphill of you to the left, each of whom will identify as ‘Hag’. The two throw some mid-level spells around, even if your own level is quite low, so this can be exceedingly dangerous for characters of less than 20th level. Once you’ve dealt with them, look to the large, roundish crag that sticks up out of the snow. Be wary, for this is Orphan Rock, and the hagraven in question camps atop it, performing various rituals. Two to three more hags lurk around the base of the rock, patrolling at literally all hours, so regardless of night or day you will need to either be prepared to sneak up on everything, or charge through massive amounts of spellfire.
The hagraven herself stays on top of the rock as much as she can, which can actually prove an advantage- her preferred spell is the explosive Fireball, and if she and you happen to both be moving as she casts it she can easily wind up blowing -herself- up with the flames, vastly simplifying your job. She is also very vulnerable to sniping by archery or spellfire due to this, as most of the locations she can be struck from that aren’t atop Orphan Rock are farther away than she has any real chance of spotting a hidden attacker.
One way or another, you’ll need to kill all the hags and the hagraven. Once you do, check the East side of the rock under the bridge for a bandit corpse- but be careful of the Frost Rune trap located right next to it. Then, ascend the slope to the East to enter the camp that the hags were staying in.
While the hags’ camp does contain some useful supplies, it also includes a human skeleton butchered down to the bones (which can be checked for bonemeal) and a locked chest with some minor loot in it. The hagraven’s camp on the rock is even more unsavory, the brazier by the hagraven’s tent containing variously-sized skulls and a small ribcage, implying that sacrifice or cannibalism of children was part of the hagraven’s habit- or possibly her magic. Search the hagraven’s enchanting table for some alchemical ingredients, her chest for a bit of valuables, the ground on the rock for a fish or two, the spriggan draped over a brazier for more alchemical ingredients, and finally the hagraven for whatever she’s carrying- plus Nettlebane.