CactiGuide.com

Hello everyone!
I just acquired this cactus from my grandmother, she was going to throw it away because it is turning brown and shriveling up. I remember this cactus used to be really green and healthy looking. I think it is the Fairy Castle type, but I am not sure. I would love to get this baby looking healthy again, any information/advice would be fantastic!
Thank you.

The brown shriveled parts should be removed Completely they are Sun burned and dead,
I have never tried to root fairy castle cuttings but I'm assuming they would do fine as cuttings and just stick them in the soil to root In a couple months, and they will grow normally, id suggest a major repot into some C&S soil and perlite (50:50)
And sift out the big pieces outta the cacti and succulent soil before mixing in the perlite you can use a grate or a small plastic 4 inch pot with holes in the bottom, and take a cup full of the c&s soil and place it into the plastic pot so the top is covered and shake it so the fine soil falls thru the bottom holes of the pot and when u start to get thick material falling thru Empty it out and reload it with soil and start over again sifting. Others will chime in soon with more help, Goodluck hun

This definately isn't sunburn, because sunburn doesn't only affect the middle of the plant, usually, only the partially shaded parts(the whole middle & underside of the plant) are undamaged, but with this one it is a disease or it's just drying up. Take cuttings of the healthy tips(5 to 10 cm would be ideal), and that means only the dark green parts. Saving the whole plant is impossible, because the main stem is already dead. Good luck with propagating!

I forgot to mention that the plant is also soft and limp. I guess I will have to take a cutting and see if I can propagate?

Yes, that's probably your best option

I agree soft and limp isn't a good sign, when curing make sure the cuttings have a nice lime green looking inside (that's healthy) allow them to dry out for a few days to callous over before potting them up, u can also swipe some sulfur powder over the wound to help it so it doesn't get infected or start to mold.

If the inside is brownish oozy coloration cut until u see fresh healthy green tissue, cause brown ooze is rot or infection and can spread, make sure u sterilize each new cut by using rubbing alcohol on the knife blade, make sure the knife is sharp and use a swift clean Motion when cutting. Don't saw it!

Goodluck hope everything works out

The damage could also just be corking , unsightly, yes! But not really a problem that would result in the plant being harmed.
I still suggest taking cuttings just in case.

Corking usually makes the plant stronger, and this one is just falling apart, so it must be a disease or a pest.

Sadly that could be so, take clippings now cause you never kno!