This is a Class 5 climb but it's short. A lot of the scrambling is Class 4. But there is enough exposure and lichenous rock to make things interesting. There are basically two parts to the route: the approach to the arête and the arête itself.
See the Main Page for the approaches. From the west side of Dog Lake, climb northward up steep talus and scree to the saddle east of North Imp. From Baldy Lake, climb SE into the upper basin between Devils Throne and North Imp. Continue up trees, talus, and scree to the 8,500-ft saddle ENE of North Imp. Turn right (south) and continue up to the saddle east of North Imp.
1st Half of Route
From the saddle east of the imp, scramble up talus through a steep, loose opening to a minor notch between two outlier pinnacles. (For a good view of the route to come, it is recommended you first climb up one of the pinnacles. The north pinnacle is probably better. Both are merely Class 3.) Take the obvious light-gray ledge west from the pinnacles for about 200 feet to a deep gully dropping to a chasm below. The walkable ledge ends here, for on the other side of the gully it becomes an exfoliated, sandy mess of steep rock. I thought perhaps a rockslide had occurred there. Turn left (south) and climb 50 feet of slabby Class 4 rock above the gully to a notch.
The right (west) side of the notch features steep mid-to-high 5th Class climbing for 30 feet to a tree that would be an excellent rappel point. You can climb this if you like or circumvent the obstacle by way of the gully on the south side of the notch. Downclimb the easy gully for about 20 feet to a stand of trees (the first trees you come to). There are two ledges that lead out on rock to the west of the gully. One is just before the trees. I did not take this one (Class 4/5). The other ledge is right on the downhill side of the trees. The first move to get up on the ledge is about 5.2 but the deck is right there, so you probably won't injure yourself. Once onto the narrow, blocky ledge, go around the corner (Class 4) for less than 20 feet toward the next gully over. You can climb down into the gully or turn right before it and climb Class 4 rock to the notch above. You should now be at the aforementioned rappel tree.
2nd Half of Route
The rest of the route until the very end follows the arête. The arête is a series of lichen-covered steps ranging from 4th Class to low 5th Class. The lichen doesn't help things, but since there's no smearing required (not that I recall), it's not all that bad. Note: I was wearing boots. Eventually, one of the steps requires a traverse out on to the north side on a small ledge (balancing Class 4).
At this point you will be at the final tower. There are two choices from here on: take a fantastic narrow catwalk with mucho exposure to a gully or continue directly up the arête. From below, the catwalk looked better than the arête. From above, the arête looked better than the catwalk.
The catwalk is about 20 feet long and isn't hard at all (Class 4) except for a loose collection of rocks at the gully end. A half-dyno step-over got me past that but I didn't relish doing the reverse of it on the way out. The final gully is loose Class 3 to the summit.
The arête continuance is Class 5.2 for about 15 feet then Class 4 along a sharpish crest to the highpoint. From below the arête appears harder than it is.
Time up = 40 minutes from the saddle, 30 minutes from the pinnacles.
I blenched on the catwalk on the return and instead downclimbed the arête. I continued downclimbing all the way to the rappel tree, which I thought I might use to rappel back to the notch. As it was, I decided to downclimb the way I came up (on the southside face and gully).
A very small rack
One or two double runners in case you want to do a rappel
Helmet not entirely necessary