Grab a Flawed Power Stone. Bring it to the Altar of Fire before the stone expires, then return to Ak'Zeloth.
The Demon Seed is a powerful tool for the Burning Legion. It rests in a cave on Dreadmist Peak, above a demonic altar of fire.
I have prepared power stones that when placed near the Seed will disrupt its connection to the Legion.
Take a stone from the table and bring it to the altar of fire atop Dreadmist Peak. Travel west, then north when the road forks. The Peak will be to your left. The safest climb to the top is on its northern face.
And hurry--the stone's power will consume itself in time.