We have sequenced Deer Mtn. with Mt. Champion and UN 13,736 for a fairly long day, ridge hike. Deer Mtn. is the third summit in the sequence, but the sequence could be run in the opposite direction of how we describe here. One-way mileage and elevation gain are measured from the summit of UN 13,736. Round-trip mileage and elevation gain assume completion of the sequence.
From the summit of UN 13,736, proceed north along the relatively flat ridge crest for a short stretch, then begin descending NE to the first of three saddles. Continue on fairly rocky & rubbly terrain beyond the saddle gaining elevation toward Pt. 13,445. This is all Class 2. About a quarter mile south of that point, the ascent will level off some at 13,350 ft. This is something of a false summit. Drop down a little to about 13,300 ft., then continue ascending north to Pt. 13,445. This last section of ridge will be a little less rocky with some stretches of low tundra showing up.
From the summit of Pt. 13,445, the real work begins with a significant notch/cleft problem to overcome. This part of the hike we will classify as Class 2+. As you descend the ridge crest, the terrain on the east side drops off dramatically. For the most part, you will stay on the west side of the ridge crest. Some fairly prominent game trails are evident in this next section that can assist in avoiding obstacles. Follow the ridge down to the third saddle at about 13,250 ft. Ascend along the ridge to about 13,425 ft. and soon after, you'll encounter a significant notch. You will have to drop down into the notch, then find a way to climb back up and out on the north side to regain the ridge crest. This will be the Class 2+ section.
Once you've navigated the notch, continue hiking NNW along the ridge crest. There will be another notch that can be easily dealt with by swinging west off the ridge a little. Conclude the ascent to Deer Mtn. by hiking and scrambling through more rubble up the summit cone. Once at the summit, there will be a nice view looking down onto the unnamed lake to the west and also of the long Class 3 NE ridge tha connects Deer Mtn. to Mt. Oklahoma. There are at least a couple reports of that ridge traverse to be found on 14ers.com and SummitPost.
For the descent, head NW down from the summit along the ridge crest. Avoid any temptation to drop south off the ridge crest until 13,200 feet. Any earlier will send you into some steep gullies where you may find yourself cliffed out. At about 13,200 feet, you can begin a descending contour down to the unnamed lake at 12,380 feet. This descent will be on mostly moderately stable talus and scree, or if you're patient and descend the NW ridge of Deer Mtn. a little further, you will be able to descend to the lake on a slope with more low tundra.
From the lake, pick up trail #1483 that drops back down into the North Fork of Lake Creek. The newer trail varies some from the older USGS map in places, but once to the bottom of the drainage, the trail follows along the west side of the creek all the way back to the trailhead. There are numerous points at which the trail cuts through willows. When you reach the TH, congratulate yourself on a job well done. This is a fairly strenuous Class 2/+ hike and makes for a longer day.
Links to other information, routes & trip reports for this peak that may be helpful.