The Evergrove Druid has asked you to collect 5 Fel Cannonballs. Once you have done so, use the Druid Signal to call to the Evergrove Druid inside of Death's Door at the Blade's Edge Mountains.
We must shut down the Burning Legion's access to Death's Door, but first you're going to destroy their two warp-gates!
The problem is, we can't even scratch one of those things, so you're going to need to use their own weapons against them.
The death's might, death's watch, deathforge over-smiths and deathforge technicians carry the ammunition for the fel cannons.
Normally it wouldn't affect any of them, but if you bring the cannonballs to me, I will imbue them with Nature's unbridled wrath!