Archmage Khadgar sends you a letter after earning this achievement.
From: Archmage Khadgar
Subject: Time to Go on the Offensive
Congratulations on your achievements, <player>! We have established a foothold on Draenor and forged new alliances with this world's inhabitants.
But Azeroth remains in jeopardy. So long as the Iron Horde churns out war machines and Grommash still draws breath, our world is in peril. Continue to strengthen your garrison and recruit your fellow heroes to take the fight to the Iron Horde and all their allies. The fates of two worlds hang in the balance.
Azeroth looks to you, commander. Do not waver.
- Archmage Khadgar