Oreocereus celsianus, and it does look rather peculiar. Check a few pics online, and you'll see what I mean.

This is present in 2-3 valleys (not sure of correct term sorry)

This is present in 2-3 valleys (not sure of correct term sorry)

{{!gwi}}

This is present in 2-3 valleys (not sure of correct term sorry)

{{!gwi}}

I'm sorry for the multiple repeat posts! Between my computer handicap and slow internet connection, I'm a mess!

Upon closer inspection, there are multiple holes (4-5)

I'm not sure what this is but its not fuzzy like mold/fungus. I'd have to cut spines off, but wonder if its mushy to the touch?

This is the closest I could find, but maybe others have a better idea.

What kind of soil do you have your plant in and is it possible for it to vacation outside for the summer? Cacti usually want a rest period in the winter so you shouldn't be watering them very much from late fall through winter.

If you do put it outside, make sure you gradually acciimate it to the brighter light.

Here is a link that might be useful: Dry rot?

Yes it will be outside this summer. Its potted in miracle grow potting soil for cacti/ succulents

I don't know about Miracle Grow, but a lot of the cactus soil sold at the big box stores have a lot of peat in them.

If you can't find cactus soil without peat--and granted, that may be hard--mix your own (search for some recipes in this forum).

I've been growing cacti for years and I still lose some. At least when you only have one, you can keep a close eye on it.

Does it look like your plant has dry rot? At the site I provided, there is a page that helps you diagnose your problem if it isn't dry rot.

The small black areas are old damage. Leave them alone; the plant has already sealed off those areas, and digging around is only going to make new wounds.

The discolouration between the ribs looks like a sort of corking, and while it's not dangerous in itself it's a sign that the plant isn't as healthy as it could be. Some of it has been there a while, as you can see from the cracks.

You don't have to cut spines off to explore the large discoloured area -- use a blunt pencil or toothpick or something to feel the area indirectly.

Outside is good (it hasn't been getting enough light lately -- see how the top of the plant is reaching up and has fewer spines?), but miracle grow anything is unlikely to drain well enough unless you have the bottom of the soil in contact with the dirt outside. Careful with that new growth though, it's especially unused to outdoors sunlight and will scorch quite easily. Consider getting a scrap of shade cloth and hooking it loosely over the top growth. Eventually that tender growth will no longer be at the growing point, and scorched shoulders are less bad for a cactus than a scorched head.

Overall the whole plant is a bit scabby, but once you get it into the right conditions you'll be surprised at how quickly that few inches of bad skin disappears into the base.

The O. trolli below is hardly a show specimen, but I'm showing it to show what the top of the plant should be shaped like, and how much increased light levels will change the spination.