Not the unicorn you were hoping for, eh ?

This particular unicorn probably didn't have much to do with rainbows at all.

For decades, scientists have estimated that the Siberian unicorn - a long-extinct species of mammal that looked more like a rhino than a horse - died out some 350,000 years ago.But a beautifully preserved skull found in Kazakhstan in 2016 has completely overturned that assumption. Turns out, these incredible creatures were still around as recently as 29,000 years ago. Yes, that means there was a very real 'unicorn' that roamed Earth tens of thousands of years ago, but it was nothing like the one found in your favourite children's book. (Sorry - it's a bummer for us, too.) 

The real unicorn, Elasmotherium sibiricum, was shaggy and huge and looked just like a modern rhino, only it carried the most almighty horn on its forehead. According to early descriptions, the Siberian unicorn stood at roughly 2 metres (6.6 feet) tall, was 4.5 metres (14.7 feet) long, and weighed about 4 tonnes. That's closer to woolly mammoth-sized than horse-sized. Despite its very impressive stature, the unicorn probably was a grazer that ate mostly grass.

https://www.sciencealert.com/fossilised-skull-reveals-when-the-last-siberian-unicorn-lived