Northern Watch is an additional survival level created for Enclave, made to become available once the Light Campaign has been completed. The map is a bit of an experimental take on the standard survival game mode, including more variable enemy spawns within each wave. The level is available from the below ModDB link, and more information about the making of this survival map can be found on the Ogier-Editor forums.

(Version 1.02)
http://www.moddb.com/games/enclave/addons/northern-watch-survival-level




Installation:
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Four files are included:
-The file Northern_Watch.XW goes in ..\Enclave\Sbz1\Worlds
-The files Campaign.xrg and StringTable_Eng.txt go in ..\Enclave\Sbz1\registry (backup the originals if you want)
-If playing the game with German or Polish language enabled, StringTable_ger.txt or StringTable_Pol.txt can also be placed in the same directory as the above files. (Thanks to DeVance for the Polish translation!)

The level unlocks after completing the final 'Vatar' mission of the games Light Campaign. If this mission has already been completed, you will need to play it again to trigger the unlock. Once unlocked, the Northern Watch mission will be available on the campaign map.