Dalaran

The city of the Kirin Tor, still on the ground beside Lordamere Lake in the Alterac Mountains. In original World of Warcraft it sat under a violet dome nobody could enter. In Forever you can go in, and something has gone badly wrong inside.

The Alterac Mountains map from the WoW Forever client — The Alterac Mountains, where Dalaran stands on the shore of Lordamere Lake. From the Forever client.

Where: Alterac Mountains, by Lordamere Lake
Rulers: The Kirin Tor (an Alliance faction in the client)
Dungeon: City of Dalaran, levels 28 to 33
New areas: Old Dalaran Ruins, The Eventide, the Fel Grove

On the map

Areas the client names in Alterac Mountains: The Eventide, Dalaran, Fel Grove.

What it is

Dalaran is the city of mages, ruled by the Kirin Tor. In Forever it's where it always was, on the ground in Alterac, and Blizzard has made it one of the nine new dungeons: a chaotic city where magic has gone wrong.

An elite cadre of the most powerful wizards in the world and the ruling conclave of magi that leads the magical nation of Dalaran.
From the game client: Kirin Tor, the faction description in the WoW Forever client

Warcraft background: Dalaran was the human kingdom of mages and home of the Kirin Tor. In the Third War Archimonde levelled much of the city on Arthas's behalf. Afterwards the surviving mages began to rebuild and shut the city behind a great violet barrier, which is how it looked in original World of Warcraft.

The City of Dalaran dungeon

Blizzard describes the dungeon only briefly: the "chaotic City of Dalaran" and "strange magical trouble". The client's encounter list fills in the tone: an Arcane Anomaly, a Fel Ancient, a Mana Devourer, a Mana Elemental and a Mana Wraith, an Unstable Sentinel, the Shade of the Archmage, Lyn the Ignored and Atrexis the Grave Knight. The client's areas inside it include Dalaran itself and a Fel Grove.

Dalaran - Faction adjustments. Spawns are now present in the area just outside the city entrance.
Blizzard: WoW Forever Beta Development Notes (Blizzard)

Speculation: Mana creatures, a fel-touched grove and the shade of an archmage suggest that arcane and demonic magic have broken loose in the city. That's our reading of the boss names; Blizzard hasn't told the story yet. The client also has a hidden faction called "Kirin Tor - Broken", perhaps for mages who have lost their minds or their loyalty.

In WoW Forever

In WoW Forever: The Kirin Tor are a new reputation in the client, and an Alliance one. The client also adds the Old Dalaran Ruins in the Alterac Mountains and an area called The Eventide inside Dalaran.

For roleplayers

An apprentice of the Kirin Tor who was outside the city when things went wrong, and wants to go back for their master.
A High Order Skyborne who came to Dalaran for knowledge and found chaos.
A Forsaken who was a mage of Dalaran in life, drawn back to the city that forgot them.
A Syndicate thief from the Alterac hills who sees opportunity in a broken city full of treasures.