According to a hi-level Japanese party, this is a NM for one of the CoP missions. And as I actually saw them spawn it and kill it, I trust them.
This bugger uses very high lvl thunder magic. Thunder IV and Thundaga III to be specific. The WAR75/NIN37 they had tanking it was getting beat up pretty badly. He simply couldn't keep his shadows up long enough to do any good. It took them about 4-5 minutes to kill it with a balanced party of lvl 70+.
i have seen them there two of them that spawn.. they took out 4 full partys.. we where doing the Rank 4 misson and they agrroed on are mage healing some one.. and they cleaned house and we where not lower level we where in the 30s and 50s and they still owned us all.. one of are mages made it to the telporter in time to let them leave and start the raiseing.. but yes they are deady and i would stay away from them unless you are level 75.. then i would still say bring a party to take them down.. who knows what they drop we did't get ether one of them down.. this has been about 3 mouths ago,, and i still watch out for them every time i pass them i am on leviathan server..
Where exactly did you see it? I camped with friends the first floor I-8 (I mean the ground floor with the zone into Qufim but in map is called 1st) and the second floor in I+J-6. 7 hours killing Chaos Idols... no NM.
The good news is that an NM so strong can easily kill the gil-farmer inside Tower, but the repop time is toooo long. ;)
i happened to walk in on this thing with my level 30 drg and my bro who is a 40 pld, we saw it whoopin a level 50ish-60 rdm ***. then we see the rdm chainspell and warp home, this thing turned around and walked in the door next to him.