The quests that will introduce players to the War Within zones are not available on the alpha, but a summary of these quests is showing up in character quest journals — revealing a serious plot twist!
On The War Within alpha, the questline that precedes the player's arrival in the Isle of Dorne — the first zone that we'll play through — is not available for testing. However, we do know some details about what happens based on context clues — most notably, the destruction of Dalaran and Khadgar's potential death.
Now, many more details have emerged with a synopsis of the story appearing on the alpha. Under the title «Visions of Azeroth» inside their quest journals, players can read a brief summary of this single-chapter campaign — including a major reveal about Archmage Drenden — the recently returned member of the Council of Six.
So there you have it. Magni Bronzebeard discovers that the Radiant Song is Azeroth — trying to warn us that Khaz Algar — a titan installation — is under threat. Dalaran is teleported to the island to help defend it, but then Archmage Drenden reveals himself to be Xal'atath all along, kicking off the attack on Dalaran.
The summary doesn't mention Khadgar's fate, or what happens to leave Dalaran in the ruined state we find it in when we arrive on the Isle of Dorne, but it does explain why someone like Drenden —