Overview
The Mummy Cooler II (sometimes just Mummy II) is the second of 4 climbs leading up The Mummy - the mountain these climbs are located on (hence Mummy 'II'). It is by far the most popular of the 4, having moderate difficulty and easy access.
Approach
Begin at the Grotto Falls trailhead. Hike a short distance (15 minutes) up the trail to the big amphitheatre on the left. Hike up the talus or snow field, depending on the season, to the left side of the amphitheatre. There are several good routes here that are worth doing to warm up on if you have time. From here either follow the trail or make your own, hiking uphill to the left, following the path of least resistance. You won't be able to see the climb until you come around a corner just before it.
Route Description
Mummy Cooler II: 150' WI4
FA:
Jim Kanzler, Pat Callis, Dougal McCarty, Peter Lev, and "Igor" - November 6, 1971
Begin the climb next to the cave where you can stash your packs. Climb up the ice, steadily increasing in steepness. The climb is WI3 for 3/4 of the climb, then finishes with a short vertical section to the top. You can escape this last section easily by stopping at the big ledge, belaying from ice screws, and walking off right.
Once you top out, look for the belay bolts on the left side. Use a directional screw for the second, as you could see a big swing for the second without it. Alternatively, head about 20 feet up to some slings around a tree if you intend on continuing beyond to Mummy III/IV
Just left of this climb is the Scepter, a classic WI5 climb.
Essential Gear
Ice screws to your comfort level, you should be fine with 6-7 screws.