Cenarius left the Emerald Dream. He had to find the true cause behind the changes affecting both the Emerald Dream and Ysera. Otherwise, there was no way to return Ysera to normal. But when he returned to Moonglade, he discovered that the Nightmare's assault was reaching beyond the Emerald Dream—they were attacking Azeroth as well.
Cenarius also discovered a serious problem: his disciple had not returned from the Emerald Dream. And Fandral, who had led the Druids back, was no longer in any condition to lead them into battle. The once-staunch Fandral was now clutching his son's corpse and weeping like a child.
Fortunately, before Cenarius returned, his daughters had already captured many of the Nightmare creatures and learned a great deal from them about how they were corrupting the Emerald Dream.
"Xavius? The Nightmare King. It seems that to cleanse the Emerald Dream, we'll first have to deal with this Nightmare King. But he may not be the one pulling the strings. There must be another force behind him—perhaps the Burning Legion. Lunara, my daughter, it seems I'll have to return to the Emerald Dream."
"Yes, Father. I'll lead my sisters and make sure Moonglade is safe."
Lunara nodded in agreement, but her other sister disagreed. Avrila went so far as to outright reject their father's plan.
"Father, I don't think there's any need for you to return to the Emerald Dream. It's so vast that your going there won't accomplish much, and you'd only be wasting your tremendous power. If you stay in Moonglade, the Nightmare creatures invading it will surely call for help from their Nightmare King. Then we won't have to look for him—Xavius will come right to us. And fighting in Moonglade would give you a far greater advantage than going to the Emerald Dream!"