A remote Pasayten Wilderness scramble usually climbed as part of a multi-day traverse with neighboring peaks (Carru, Osceola, Blackcap) rather than as a standalone day trip.
Drive the Hart's Pass Road past Hart's Pass to the Slate Pass Trailhead (about 6,900 feet) — one of the highest trailheads reached by road in Washington, though the road's condition varies year to year. From Slate Pass, follow the Robinson Creek/Middle Fork Pasayten trail network into the central Pasayten, with established campsites at the Robinson Creek-Berk Creek junction, Fred's Lake, Lake Doris, the eastern head of Eureka Creek south of Lago, or a bench around 7,500 feet southwest of Shellrock Pass that serves as a good staging camp for several peaks in the area. From a suitable high camp, approach Mount Lago's south side and scramble the south slopes to the summit; this is typically combined with an ascent of neighboring Mount Carru from the same camp.
Descend the south slopes back to high camp by the ascent route.