Gates of Discord
Gates of Discord was released on February 10, 2004. It added the Berserker class and the continent of Taelosia, and it is remembered for one of the hardest raid progressions in the game.
What it added
The Berserker class arrived with this expansion. The level cap stayed at 65. The new lands are on Taelosia, a stormbound continent across the Abysmal Sea, reached by the Wayfarers’ ship from Nedaria’s Landing.
The story
It begins with the visions of the mage Calliav Giniuar: a dark land across the sea and an army waiting there. The Wayfarers Brotherhood sailed the Queen of Thorns to find it and found the native city of the nihil in ruins, held by the Legion of Mata Muram. See Taelosia and Mata Muram and Mata Muram and Discord.
The road through Taelosia
You land at Natimbi, fight through the ruined city of Qinimi, Riwwi, Barindu and Ferubi, and on to the northern temples of Kod’Taz, Yxtta and Qvic. The progression ends in Txevu and in Tacvi, Seat of the Slaver, where the Tunat`Muram Cuu Vauax waits.
Sources: Allakhazam: Progression in Gates of Discord · Allakhazam: Berserker · Allakhazam: EverQuest Expansions · Wikipedia: EverQuest expansions