Replant it of course.

It looks like some type of Euphorbia. Be careful with the sap. Some people get a poison ivy-like rash if the Euphorbia sap gets on their skin.

That thing is going to be very difficult to move and replant on a steep slope. This is a time for plant propagation with a succulent like this. Basically, cut all the branches off the single trunk so you can move them carefully to a shady spot where you can let them dry out for the next MONTH. After they have cured you can plant all your new babies on that slope.

Someone else may have finer details on the procedure, but that is the basic process to save and multiply this plant.

And yes, the sap. Just wear work clothes that keeps all of you well covered. You'll live.

I have scars from a Euphorbia rash. Yes there's a wide gulf between death and permanent disfigurement, and I think most people try to avoid both. Not to mention 10 days of misery and no sleep from itching like crazy. I have several various Euphorbia plants, and lots of other plants that have latex sap, like Ficus and Hoya, but I am careful to avoid the sap and wash immediately if some gets on my skin.

I had the same thing happen after a wet winter a few years ago. I gave up trying to replant the whole thing. I cut off the top 4' or so and stuck that in the ground. Do you know,it's taken 4 or 5 years to show new growth? It was not a fast re root. Could be just my watering or some other reason to take so long.

Looks like a Euphorbia Ammak. They seem to take forever to root. I have best results with small sections of a foot or two. Any bigger may not take. If you re-right it, you will need a large pole to support it. Sort of like tying it to a telephone pole. They are expensive and could sell cuttings on Etsy or Ebay.

Keep a water hose handy to wash off any sap and wash the cut wounds to stop it from bleeding out. If you get the sap in your eyes, it could cause blindness so please be careful. Flush with cold water for first aid.