this is an attempt (maybe better than nothing).. but please excuse me if im wrong about particulars
When you buy nightfall armor, it has no stats like <+5 when controlling 1 minion> or anything like that. Just the AL, and the inherant energy bonus for each class. You can then buy new runes like Vitae and Attunement if you want some added energy or health at the cost of your other minor runes on your armor. there are also ones to help with certain conditions, but i dont know the names. Then you can get insignias. Think of them like runes, but they dont overwrite runes. You get an insignia, you apply to a piece of armor, and whammo, there's your complete armor. you CAN put an insignia and a rune in one piece of armor. And Vitae runes DO stack with Vigor runes just not in the same piece, obviously

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anyway, hope that helped a little