I honestly thought people were just making it up until I noticed it on the map in Western La Noscea near the Magic Pot. It's a level 41 boss FATE with an adorably oversized Scrambling Spriggan! It actually killed us initially but thankfully some helpful FC-mates came to assist. Everybody got a Gold Egg from it.

Before:


After:


No idea what the repop timer is like but it was fun!