Hike from the Lake Agnes Trailhead to Lake Agnes. Circle the lake counterclockwise. When you get to the west side look for a talus slope. Ascend this below a cliff face to the basin containing an unnamed lake. The talus is well packed and not loose so the going is easier than it looks from below.
When you get to the unnamed lake, circle around its north shore to the west side. You'll see a grassy slope leading up to a ridge that extends from Mount Mahler's north face. Climb this to reach the base of the north face.
From here it's a long, monotonous, talus slog to the summit. It doesn't really matter which path you choose, just go up! The talus is loose in places, but the only real danger is rolling an ankle. Be careful.
I recommend trekking poles for ascending the talus. Otherwise just bring standard gear for hiking in the mountains.
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