This mob is a big mushroom. We were exploring and only had one high level group. Needless to say we didn't expect to take it down, but it was the end of the night... While clearing some of the mobs in the back of the room before the main pull, we either agro or baf'd Rotoddjur.
It promptly spawned 4-5 smaller mushrooms (purple to 50). These mushrooms were able to take out our Level 50 Warrior in about 8 seconds after which our group promptly did a nose plant.