Though claimed at times by Valenwood, the Gold Coast, and Hammerfell, the island of Stirk is really a no-man's-land. If it belongs to anyone, it's the Pirates of the Abecean Sea, who use Stirk's Ayleid ruins as arenas for settling disputes through trial by combat.
Stirk
Stirk is an island off the west coast of Cyrodiil. It is considered neutral territory.
You will visit the island during the related quests at the conclusion of your alliancestoryline in order to access Coldharbour. The island has no wayshrine or map marker, and it is not possible to return following the end of the quest.
The Ebonheart Pact's camp is set up south of the meeting site. Red, Pact-style tents are set up around the premises. Companion Elites guard King Jorunn. The Daggerfall Covenant is situated to the north of the meeting site. Lion Guard Elites guard King Emeric's camp. Altmer-style tents decorate the Dominion camp east of the meeting site. First Auridon Marines stand guard over Queen Ayrenn.
The Stirk map can be viewed by clicking on the island from the Tamriel map, though it has no outline or label. Prior to Update 45, the island could not be clicked on from the world map at all.
During Justice for the Fallen, a portal to Stirk will be opened within the Mages Guild in Shornhelm. It remains open following the conclusion of the quest, allowing for permanent access to the island.