On normal servers, when you attempt to kill some NPC of the opposite factions, two very bad things can happen:
1. The factional NPCs can attack you, and you will not be able to attack them back due to the "Invalid Target" message. e.g. attacking Astranaar
2. The factional NPCs PvP enable you, and surrounding players of the opposite faction can burn you into the ground. e.g. attacking Orgrimmar
The solution lies within the use of a pet. Usually this pertains to either a Hunter or a Warlock, but there are many instances where another player can summon or use a pet through an item or trinket.
So here's the thing. To be able to attack these NPCs, you put your pet on defensive, and let the NPC aggro you WITHOUT attacking it. A warlock can use the Health Funnel to heal their pet, as a hunter can Mend Pet. In this way, you can continally heal your pet, and kill as many NPCs without being PvP-ed. This can be very useful when you start out raid on major cities, you can have pets kill the guards and also have the abilty to resist ...well....resistance from the opposite faction.
I personally am a 60 Undead Warlock in the server Skywall, and use this strategy when raiding Astranaar or other Alliance cities where A. I cannot attack the NPCs or B. keep getting killed by wandering Alliances packs.






