That's exactly the message I wanted to convey: this creature should be incredibly rare and not reproduce on the map. If it only appears in the Temple in a single instance, it can be made a "mini-boss."
Added after 9 minutes
There's no need to break the entire system. Take all the abilities in the game, throw them into a blender, shake them up, but don't mix them. Then, apply the resulting mixture to the creature's stats, and you've got a boss.
Of course, it would create a creature that could guarantee victory in any argument against "Uncle Karate from the neighboring apartment building." And finally, it could settle the debate of "who is stronger, Jackie Chan, Schwarzenegger, or Spider-Man." But again, we're not five years old, are we? Why create an invincible monster?
Imagine the "joy" players would feel when encountering such a creature. Of course, fans of Korean MMOs and other min-maxers would appreciate it. It would take three days of real time to level up enough to defeat a single Kraken boss. But I'm not one of those, and I don't find that kind of gameplay appealing.
Added after 3 minutes
The moral of the story is: let's make it powerful, but not so powerful that it encourages players to min-max. The task isn't that easy, as is any balancing decision, and I wouldn't mind some help with that, so I'd be glad if anyone has any ideas.