Quests in Burning Crusade Classic require Black Morass as a prerequisite.
The Black Morass
This quest chain begins with To The Master’s Lair from Steward of Time in the Caverns of Time and requires first passing through Old Hillsbrad Foothills to access The Black Morass. More information on how to complete these phases may be found on the Old Hillsbrad Foothills quests page.

66 is the minimum level.

NPC quest

Andormu, Caverns of Time, /way 41.8 38.4

Ends: Sa’at, near the entrance of The Black Morass.

Rewards:

Keepers of Time have a reputation of 1250.

1,250 experience

Quests in the Black Morass in the Burning Crusade Classic

The Opening of the Dark Portal
Defend Medivh until he is able to activate the Dark Portal. He hands you a Chrono-beacon, which you may use to summon a time guardian to help you.
66 is the minimum level.
NPC quest
Starts/Ends: Sa’at, near the entrance of The Black Morass.
500 reputation with the Keepers of Time
25.300 experience

Hero of the Brood
Return to the infant, Andormu, in the Tanaris desert’s Caverns of Time.
66 is the minimum level.
NPC quest
Begin: Sa’at, near the entrance of The Black Morass.
Andormu, Caverns of Time, and /way 38.8 41.8
8,000 reputation with the Keepers of Time
1,250 experience

Black Morass Chained Quests in the Classic Burning Crusade
The Master’s Touch
This is the sixth stage in the Karazhan Attunement quest line, and everything you completed in the previous Black Morass quest lines will fulfill this prerequisite for you. You only need to complete the following quest that you receive after completing Hero of the Brood.

This quest merely adds the requirement of speaking with Medivh at the end of the dungeon to activate the Restored Apprentice’s Key.

Level Requirement: 68 Quest NPC
Begin: Khadgar, Shattrath City, /route Ends: Medivh, Black Morass, south near portal, 54.8 44.6
350 reputation with The Violet Eye as a reward
25.300 experience

Return to Khadgar
Return to Khadgar in Shattrath City and hand over The Master’s Key to him.
Level Requirement: 68 Quest NPC
Starts in Medivh, Black Morass, and near the gateway in the south.
Khadgar, Shattrath City, and /way 44.6 54.8
Rewards:
The Violet Eye has a 500 reputation.
19,000 experience

Profession Quests in Black Morass in the Burning Crusade Classic

Master of Elixirs
Get 10 Essence of Infinity from Rift Lords and Rift Keepers in the Black Morass in the Caverns of Time. Bring them to Lorokeem in Shattrath’s Lower City, along with 5 Elixir of Major Defense, 5 Elixir of Mastery, and 5 Elixir of Major Agility.

This task is exclusively available to Alchemists. Elixir Master is the second step in the Master of Elixirs sequence.
Minimum Quest Level: 68 NPC
Lorokeem, Shattrath City, and /way 45.8 21.0 Reward: 250 Lower City repute
25.300 experience
Elixir Master