More on E. flanaganii. http://redlist.sanbi.org/species.php?species=574-126

Your plant’s details are a little blurry to tell for certain. I’m speculating from plant’s shape, it looks like a species of Euphorbia called Euphorbia flanaganii (Medusa Head). In my search I found it sometime misidentified as Euphorbia caput-medusae. According to sources E. caput-medusae has white flowers, while E. flanaganii has yellow. You will know for certain when yours blooms. I’m not an expert on Euphorbia and found its synonyms are also not clear enough to list them, I will leave that to the experts. Check it out and see if you have a match. Best wishes! https://commons.wikimedia.org/wiki/File:Medusa%E2%80%99s_Head_(Euphorbia_flanaganii)_2.jpg