Little background.
When FFXI came out, there was an ability everyone had access to which was called check. Now check just gave an idea of the level range. So you had mobs that were too weak, easy, decent challenge, even, tough, very tough, and impossible to gauge.
Now this only gave you an idea of their level, it didn’t mean anything about how strong they were. So a mob that was level 1 could still kill you if it had the stats to back it up.
Anyway, I had unlocked beastmaster, and there were many, many fun things you could do. One of which, was charm various monster NPC’s.
So one day, I took one of the mobs which was about level 20 or something, and stuck him just outside one of the capital cities. I then released him…and ran like hell.
Mob agro worked differently in FFXI when it first came out. So if you left a mob in the zone and it was agroed, it would often kill anyone who was nearby.
Lo and behold I left my quest mob in front of the gates. A player of 30 would see it, check it, attack it, then DIE.
Anyone who came out of the city in that moment? Also dead.
The monster leash was zone based, so until someone killed it or leashed it out of the area it stayed right where it was, happily killing anyone who came out.
My friend did the same thing on his BM, and then he ate a GM penalty of 3 days. Brutal.
Another time in a game called Istaria, my friends and I got bored. We then dragged an epic monster of level 120 named Fenrir and left it in the main capital of Bristugo with all the portals. Hilarity ensues.
Mobs in that game didn’t have a leash. They stopped agroing ONLY if the player escaped their distance.
So…yeah…we dropped the equivalent of Mythic Azshara on an unsuspecting city where it stayed killing people for a few hours.