This route is big day out. Aspiring ascentionists should see David Jones' book "Selkirks North" by Elaho Publishing for a complete description.
We did this route all free in a day during August 2007 with a new variation on the lower tower. The first ascentionists gave it 5.10+ A1 and did the route over two days. Ours was the third all-free one day ascent, and likely the fourth ascent overall.
Three distinct "towers" or steps comprise this route. The route stays almost entirely on the crest, save a bit near the top of the first tower that wanders around to the north.
The first tower has the best splitters on the entire route and a difficult, long corner will likely be the crux for most.
The second tower is very steep and has lots of loose and dangerous rock. There was likely a major rock-fall here in the recent past. The climbing is still very good and physical, albeit a bit heads-up.
The third and final tower ascends directly on the crest and features some spectacularly exposed knife edge climbing to a traverse under a massive roof and some easier fifth to the summit.
This route is stunningly classic and I'd give it four stars if not for the shattered rock on the second tower.
The Route ascends the prominent buttress of the Horn. Start up a large gash/chimney on the right side of the lower part of the toe of the buttress. Ascend the gash to a large vegetated ledge to the true start of the route.
To descend from the summit (Depending on where your camp is you will have several options) descend to the east with one or two short raps. For a camp in the Horn/Unicorn Basin(our choice), traverse to the north, tagging the summit of the unicorn and over the other side. Continue along the prominent ridge between the Horn basin and the Granite Glacier basin. Once to the saddle, descend to the west to the lowest point of a large snow field above a cliff band. Two to three raps and some scrambling down the slabby cliff band will return you to the upper Horn basin below mount Colossal.
Double cams from blue alien to #2 Camalot and 1 each of #3 & #4 Camalot. Single 70m rope OK for committed parties. Retreat from the upper pitches would be very difficult.