The suggestion re: freeing Dark Void is intriguing. Currently, Darkrai is seen only very rarely on the SM DOU ladder and almost never past the 1400s. It's usually running Hypnosis, which is hit or miss, but only has one target. Obviously, there are many Pokemon who sometimes run Hypnosis and its effectiveness is greatly hampered by the presence of Tapus Fini and Koko, which are used more and more frequently the higher you get up the ladder (the vast majority of top teams have one).
So my initial reaction was similar to Veecy's. What harm can a move that only has 50% accuracy do on an otherwise suboptimal mon? Then I started thinking more about how this could play out. Hypnosis is really most dangerous (and only viable on the ladder) when its accuracy is boosted. The most prominent example of this is Purple Rain Lele's Trick Room team, where Bronzong uses Z Trick Room to immediately get speed control and an accuracy boost. Of course it's backed up by Lele who gets rid of pesky Misty and Electric Terrains.
Most of us SM DOU ladder denizens are also at least familiar with Coil, which can, for instance, turn Milotic into an accurate sleep inducer, but Milotic is slow and not great offensively, so the strat is pretty fringe. Imagine, however, that you get off a couple Coils on a bulky Milotic (or Zygarde), then switch into Darkrai as safely as you can (e.g., through a slow Incin U-Turn). Next turn you could use Psych Up on Milotic (which Darkrai gets of course). Then you'd have a pretty dangerous mon on your hands that is very fast and likely puts 2 mon to sleep each turn (of course, you'd need Tapu Lele or Bulu in the back to get rid of inhospitably terrains). Psyched Up Darkrai would have a great defense and its offense is already good. It could have significant HP and/or SpD investment, as well as Speed, and run Sash or a berry to be safe. Then, after it has put its targets to sleep the following turn, it could use Dream Eater (maybe boosted by Psychic Terrain) or Drain Punch (when your Attack is +2 going physical becomes a real option) to recover its health. Bad Dreams would also take their toll on the sleeping victims each turn. Not the easiest set-up, but if you could pull it off it might be pretty good. (Edit: That example is just the first thing that came to my mind late last night and I think Darkrai is potentially better than other Psych Up candidates because of its ability to essentially knock out the whole opposing side before they have a chance to react and to later recover its health while dealing significant damage. However, Sweet Scent, which is almost never used currently, would definitely be easier to pull off, as Memoric noted, and Memoric's post hints at the existence of other methods (e.g., Z Move to increase accuracy followed by Baton Pass--and Mew and Shedinja get Hone Claws and Baton Pass). There are certainly other ways to effectively boost accuracy a little bit (and every bit helps) as well, but 50% times 2 is already clearly much better than 60% times 1 and Darkrai has incredible speed to make use of that--you very likely get 1 mon asleep and Bad Dreamin' and you might get 2, so raw sleep fishing could be viable. Anyway, I think my point stands that there's some chance, especially given players' resourcefulness in developing strats, that freeing Dark Void could have a noticeable impact on the Meta and it could certainly make it more critical to carry Fini or Koko on the ladder.)
Maybe I'm missing something here (I just saw this post and it's very late my time), but I'd definitely be open to a suspecting Dark Void (a suspect of any kind on the SM DOU ladder would be awesome!). I think we just need to think about how it could actually be used by a skilled player before we unleash the Void.
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