I recently completed the Bros. Before Ho Ho Ho's achievement on Gillien at level 71, because I couldn't stand the thought of having to wait until next year to get the Merrymaker title. But there's a slight problem for us Horde.
Brother Keltan is in Icecrown, and not only that, but he's on an airship! Summoning doesn't work (poor sap my guildie tried to help wound up in the Argent Vanguard instead), so what's a Hordie to do?
For those of you who are like me, and tried following the instructions on WoWHead and still couldn't quite figure out if you were in the right spot, I've put together a graphical how-to.
You will not need anyone to help you with this and in theory you could do this as low as level 1, though I'd hate to see the corpse run on that one!
First! Make sure you have your Mistletoe. It would suck to get there and find out you don't have it.
Second! Do yourself a favor and buy a few Dark Runes. Supposedly it's possible to do this without any, but save yourself the aggravation and buy some. It'll save you a lot of time and corpse runs. If it turns out you don't need them, just put them back on the AH for the same exorbitant price you paid for them (or more!). I bought four for 20g (5g a pop) and due to me being fumble fingers I actually used three. If you find you need them but can't buy them, they drop in Scholomance. Have fun with that.
Next, follow the route on this map (click on it to see the full-size version). See that little tombstone where I died? That's where you want to be.
What you need to do is ride up to the Argent Vanguard in Icecrown via the road from Crystalsong Forest. Ride through the Vanguard and into the narrow canyon full of nerubians. You'll emerge from the canyon and find a nerubian base in front of you. You'll have to ride north towards and then around (circling west) the northeasternmost ziggurat. There's a narrow path behind it that will take you to Sindragosa's Fall.
Ride through Sindragosa's fall. You don't really need to hug the mountains to your right, and depending on your level it may behoove you to leave as much room between you and any mobs as possible. The important thing is to head north to where a wide snow path leads up and over the mountains to the other side. You'll know you're on the right track if you see the northern ocean and penguins.
Once you're up on the northern side of the mountain range, follow the wide snow path until it starts to curve back to the south. Don't follow it too far south or you'll fall and the only way back is to ride around the mountain range again.
Just before the steep fall you should see a sharp stone outcropping. This is where you're going to position yourself.
It's a steep outcropping, but it's possible to run up it. From where you see my body you can repeatedly jump off to the north (screenshot is facing southwest). This way you should not fall too far, and you can better control how much falling damage you take. You don't want to jump downhill or you'll risk sliding down the slope and dying too far down.
I found that if I mount up and jump off in a somewhat uphill direction, I could get smaller increments of damage, which is good because if you want to use the Dark Rune method you'll want to get to less than 600 health without killing yourself.
Some people apparently can kill themselves on the mountains around here without using Dark Runes. If you're a warlock, all you'll need to do is stand where my corpse was and Hellfire yourself to death. If you're like me, keep jumping until you're less than 600 health, less than 400 to be safe. Then quickly run high up on that outcropping and use the Dark Rune, making sure you have less than 600 health when you do.
If you didn't screw up, you'll die and this will be the only death you'll have to take.
Fly on the spectral griffon back to your body and then wait over the snow path beside the outcropping. Eventually the airship will come (it takes between 20-30 minutes to make a circle and you can see its location on your mini-map). It's very slow so you'll see it long before you can climb abroad, and it's terrible waiting and wondering if you did it right! But hopefully if you died where I did you'll find out that the airship actually does sink fairly low to the ground at this point and you should be able to fly into the bottom floor, the cargo hold as it were, and once it's close enough to your body you'll be able to ressurect.
And then bingo! Brother Keltan walks clockwise in a circle around the ship. Find the stairs from where you are in the bottom, and start moving in a clockwise circle up the stairs, across the deck, and back down again and you should bump into him.