North Cotter is the prominent horn located just north along the ridge between Mount Cotter and Clarence King. The Northeast Arete
of this subpeak is a classic Sierra ridge route, included in Moynier and Fiddler's Sierra Classics guide.
From Sixty Lakes Basin, gain the prominent ridge via slabs and easy scrambling. Avoid steeper climbing low on the ridge by traversing talus and ledges
on the right (north) side of the lower ridge, regaining the ridge at a prominent notch near the base of the steeper, upper arete.
From the notch, traverse the narrow class 4 ridge
to where it steepens. The rock is more featured
than it appears from far below. Continue along the steep arete, staying to the right when difficulties dictate. In general, the rock quality is better directly on the arete, but climbing is more difficult. Sustained exposure and frequent 5th class moves make this a thrilling and enjoyable route, while occasional small ledges on the right side of the arete offer momentary respite.
The descent is the crux. You have at least two options.
(1) Downclimb and/or rappel the route. Note there are no fixed rappel anchors along the route.
(2) A more serious option is to traverse the ridgeline to Mt Cotter's main summit. Walk to the south along the summit ridge to where it drops away on all sides. An awkward entry to a short 5.6 downclimb on hideously exposed flakes marks the technical and psychological crux. Another 100 feet or so of sustained, exposed class 4/5 downclimbing
on the knife-edge eventually leads to the saddle between the peaks. Note that it may not be practical to rig a suitable rappel anchor for this section. From the saddle, follow class 3/4 ramps
up the right (west) side of the ridge to where it steepens into a short class 5 section. Cross over to the left side of the ridge and scramble up easier terrain to the true summit. For a more pleasant and aesthetic return to Sixty Lakes Basin, follow talus and huge boulders directly on the crest of the East Ridge as long as possible, avoiding the scree and sand to your right.
If choosing to solo the route, bring a good pair of shoes and a calm head. If belaying, a light alpine rack is sufficient.