Use the Naturalized Ammunition to take control of the Death's Door
Fel Cannons. Use them to destroy both the South Warp-Gate and the
North Warp-Gate. Then, use the Druid Signal to call out to an
Evergrove Druid to report your success.
Now that the ammunition can affect the Burning Legion, it's time
for you to use it.
There are two warp-gates, which are used for teleportation and enhancement
of the void terrors. One is in the south and the other in the north, and
each is within range of a fel cannon.
Use the naturalized ammunition to take control of each fel cannon
and destroy the warp-gates.
Attack the gate with artillery to begin, and be prepared to kill
its defenders to keep the cannon alive if necessary.
For Frost Mages, its best to use your Ice Lance on each Unstable Imp. It takes two shots (one if it crits) to kill each one, which allows you to continue using the artillery shot, as opposed to the anti-Imp round. Make sure you have Mana Gems conjured!
You might have learned about destroying the Forge Camp equipment during some missions in Nagrand.
This is really a "friend or two recommended" quest...
When you use the Naturalized Ammunition, you gain the cannon as a stationary pet, complete with pet bar. On that bar are two special abilities: Fire on the Warp Gate, and Flame Thrower. Both are
on the same timer, so any use of one prevents you from doing the other until the cooling time (about 15 seconds) is over. A pet-using class such as hunters and warlocks (and to a lesser extent, mages and druids) should note that using the cannon, it becoming a pet, will dismiss your permanent pet until you summon them back afterwards.
It takes 7 shots to destroy a warp gate. The moment you start firing, a series of suicide imps start emerging from the gate. They explode for perhaps 600 points each, and appear in a fairly steady stream (perhaps 2 seconds apart). Five or six of these blowing up next to your cannon will destroy it, so you must intercept them short of the cannon. They have about 500-600 HP, and will explode next to you if you aggro them. Their explosion replaces their melee attack, but does not happen when they die. This can be completed solo, and is easier for some classes than others. Rogues, for instance have the hardest time with this quest.
The key to victory is to stand n the way of the imps and use a low-mana instant cast spell to kill them. Another idea is to aoe them down, and depending on the range of your aoe, this may or may not be a good idea. The bigger the aoe, the better an idea it is.
Meanwhile, some time during the process, a corehound look-alike dog wanders near the gate, becomes "unbanished", and attacks you. A standard mob, but he'll distract you while you are fending off the line of imps. Thus the "friend recommended".
If you're a melee class, this quest is piece of cake. Simply walk slightly backwards as you hit an imp, and they won't hit you at all. If you're a warrior, the key to victory is Victory Rush.