I had something similar happen to me in Crushbone once upon a time.('05?)
Chanters have the ability to do a lot of pranking. A classic is to charm some trash mob and then buff it up (helps to have an cleric bot or friend), maybe including a damage shield, equip it with some weapons and then break charm and let the mob go back to its business. First clueless players than engages gets a BIG surprise!
I had gone up there to get the SBS from the trainer. At the ZL, I aggroed an centurion thinking I'd just plow through him on the way in.
Nope. I hit and hit and hit ad nauseum before I brought him down.
Some wise guy had givern him the pet HP belt.