I am proposing an area based on the ORIGINAL Vyxnaar lair in Pocket Legends.
This would be accessible through a hole in Kraag and would technically be a Level 16 area. All mobs would be Level 16 and would be infinitely re-spawning. Their respawn rate would be based on the average time for a level 31+ to clear to the entire area with no Beasts present, so might need to be adjusted at the beginning, but copying the respawn rate of the mobs in Vyxnaar's lair would work to start.
Now the Beast? What is it called, and what does it look like? That I leave to the players ... [FORUM CONTEST]! But the Beast would need to be a Level 36 ELITE, and would need a healthy respawn rate. Again, the respawn of the ORIGINAL Vyxnaar is a good example. Usually takes about 3-5 minutes of killing to get him to appear, but because it is a roll you can run into 2 or more at once.
The Loot: The basic loot would be general level 16 items, including crates. He would also have a chance at pinks, but those pink chances need to be EXTREMELY LOW, as in the lowest in the game. Those pinks will drop though, from re rolls. The reason their chance needs to so low is because he would also have an infinitesimally low chance at a Mythic Egg! What would the Egg be? Why, a miniature version of itself, of course! This is why the Pink Chance needs to be Barely above the Mythic Chance to allow luck to have an edge but not a drowning affect.

So, why would this be fun? Same reason Vyxnaar was, it is a playground. Running around whacking weak mobs till a Beast shows up and tangle with him, then rinse, repeat. Only issue is it is not an instant gratification area. This Egg would be EXTREMELY hard to get, especially now, but will get easier as players level up, and after new caps they can try him again.