Not sure if still possible, but some skills allowed you to bug outside the map. Getting into inacessable spots. Sealed mobs didnt attack or move in those spots and could be mass killed with AoE like berserker auto attacks.
Used to mass spawn them in A6 for the mats dropped there, and left the map using renegade's dash
While you can attack without issues you cannot pick up all the items without packets if in such a spot.
Ofc this can get you banned if caught