TheWoWDBUsing the scroll at the portal teleports you to Outland, Hellfire Peninsula, near where Kazzak spawns.
The quest text doesn't mention this although the tooltip on the scroll does. Be warned, there's no instant way of getting back to the Isle of Quel'Danas if you take this quest, the portal does not let you return.
Quest
The Missing Magistrix
A World of Warcraft quest in Isle of Quel'Danas. Facts and objectives from the current retail game data.
The highest voted Wowhead comments for this page. They are community notes, not TheWoWDB comments.
Portal is /tloc 48.5,44.4
This quest appears to be unrepeatable. Meaning, the second and subsequent days you must actually travel to HFP.
Quest facts
LevelLevel 25-30
Quest ID11526
The client quest POI data records no map location for this quest, so no map is shown.
Check whether you have already completed this quest
in-game: /run print(C_QuestLog.IsQuestFlaggedCompleted(11526))
Description
We sent one of our operatives to investigate the fel portal in the middle of Dawning Square, south of here. She never returned. Take this scroll we found on one of the enemy corpses. We believe it will grant you access through the portal. Once through, find Magistrix Seyla and aid her in any way you can.
Community notes from Wowhead · 26 comments
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Reward details
Reputation: Shattered Sun Offensive +75
Shattrath City's final push against Prince Kael'thas' operations in the Sunwell.
Reputation group: Shattrath City.
Other quests in Isle of Quel'Danas that reward Shattered Sun Offensive reputation: Crisis at the Sunwell (+10), Duty Calls (+10), The Sanctum Wards (+150), Arm the Wards! (+150), Erratic Behavior (+150), Further Conversions (+150).
Item facts are the current retail client’s (ItemSparse); the specialisations for a pick-one item are the ones the Blizzard quest API lists; faction and currency text is the client’s own. Lowest listed price = the US commodity auction house now.