The Sun Gate is a portal located near the Vector Coil in Bloodmyst Isle [18.9, 63.5]. The portal was opened by the Sunhawks, servitors of self-proclaimed Sun King Kael'thas Sunstrider, to allow blood elf reinforcements from Kael'thas' fortress of Tempest Keep to enter the Azuremyst Isles, with the intent of retaking the Exodar. The portal, which never closes, shows the front of Tempest Keep, of which the Exodar was originally a part (hence why Kael'thas is sending his servitors to retake it).
Draenei players - after doing a series of quests pertaining to it - will ultimately be called upon to destabilize it, sealing off the entry point for Kael'thas' legions to enter Azeroth.
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