I would keep the shadow field. It makes archons pretty tough at 500pts. I would also drop the sails they not bring anything to this list. Also so that your list is 499pts, being 9pts over is a lot, most clubs won't let you go over the allocated points limit, tournament definitely won't so it's good to get into good habits from the get go. I would also drop the night shield to give your warriors a splinter cannon.
Hope that helps.
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