So you Nightmare a Damsel so that the AI will play them all. Then you heavily armor, Purify, OD, Quint and SoW it. It's too bad you'll be taking damage from all but 3 creatures. Compare with having your own Quinted SoW'd OD'd creature and you're left with a deck that can block a total of 3 creatures, helps your opponent draw more and is prone to bad draws. Weaker than a normal SoW Mirror deck against the vast majority of x2 draw decks, but stronger against the decks it's already strong against (which is pointless because it basically always wins those matchups). Sad but funny :>
(Gemriders are better)