To clear up any confusion or answer any question people have:
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Little English Halo Blog w/ tweets from David Ellis
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-There are only 8 different specializations.
-Everyone, everywhere, gets access to all 8 specializations.
-If you buy the regular edition of the game, you get access to 2 specializations after you’ve hit level 50. (wetworks and pioneer) Pick one, level it up, and then pick another.
-If you buy the LE, you will get access to all 8 once you hit max rank. As with the regular edition, pick one, level it up, and then pick another. The only difference is that you can choose from all 8, not just from the two.
-There are 10 levels per specialization.
-The first 9 levels unlock armor permutations, armor skins, a weapon skin, emblems, and a visor color.
-On the tenth level, you unlock the armor mod described in the article. You now have access to it at any time.
-343i chooses when to unlock the next specialization for all to enlist in. They will be watching to see when players are hitting max rank, and will unlock them accordingly.
-You must reach max level (50) before re-enlisting in one of the 8 specializations. You will not be able to access any right away.
-You can only have one mod equipped at a time.
-When you re-enlist in another specialization, you do not lose everything you’ve earned before.
-You do not have to wear the armor to use the mod.
-The mods unlocked through completion of each specialization are tactical/support mods. They just add to the category they belong in, they aren’t something separate.
-There will be multiple playlists that do not utilize armor mods unlocked through specializations.
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I will update the OP if I come across more information. Feel free to suggest some, or correct me if I am wrong.