I found him yesterday, 22:00 server time, in the canals between The Park and the Cathedral square. This was not on the server I have my main, so I was only lvl 5, though.

I warned two lvl 70 hunters and told them about the beast, but both of them said: LOL, a creature like that doesn't exist, and rares are never tamable, noob.

I knew this was bullshit, so I warned a lvl 60 hunter instead. He came quickly and tamed the beast. He gave me 25 silver as a reward for warning him, which I spent on beer at once.

This was on Boulderfist, by the way. Happy hunting!