Night march though. Even with Vileplume it still kills this thing.
Not so much against a T1
Vileplume, which
Forest of Giant Plants makes a possibility. Not sure if that is the route I would take, but I am just throwing it out there as a possibility.
Night March has its vulnerabilities. Not saying it isn't one of if not the best deck in both Standard and Expanded right now, but we have the beginnings of a deck that should actually have a solid match up against it. The trick to remember is
why you'd focus on
Darkrai (
XY: Black Star Promos XY114). Its "Dark Cutter" attack is mediocre so we are trying to optimize its "Abyssal Sleep" attack instead, right? First let me focus on that, then I'll suggest how we might handle Night March.
Vileplume (
XY: Ancient Origins 3/98) does seem like the correct call to me. Unfortunately, we also should probably try to squeeze in
Silent Lab as well. Your opponent will need the Ability off of a non-Basic Pokémon or else a Supporter to get out of being stuck Asleep in the Active slot. I don't know if that means running a split between
Silent Lab and
Forest of Giant Plants or just not striving for a first turn
Vileplume. I also don't think a first turn
Darkrai is that important either; if the rest of the stuff works, your opponent shouldn't build up too quickly either. That means we could open with good ol'
Yveltal (first released as
XY 78/146): use "Oblivion Wing" to soften up whatever is Active (maybe even take an early Prize if said Active is small) while building
Darkrai on the Bench. When
Yveltal falls or it is worth retreating it, switch to
Darkrai. Abyssal Sleep (preferably with either a
Muscle Band or
Fighting Fury Belt attached) will then go for 2HKOs against presumably helpless foes. Your opponent will get a chance to counterattack anytime you take a Prize, which makes
Fighting Fury Belt preferred.
So about Night March... if you've got
Yveltal and
Vileplume, you should have what you need to deal with it. Night March has to go first and get a really good set up, otherwise you shut down Items,
Shaymin-EX, and
Mew (
XY: Fates Collide 29/124).
Joltik and
Pumpkaboo can score OHKOs if the opponent has about six Night Marchers in the discard pile, but
Yveltal can OHKO them right back for just one Energy, and
Darkrai for two (which if
Yveltal leads, isn't a huge burden).
If Items and Basic's Abilities are locked down, this does
not leave a lot of wiggle room for Night March. Even with all four
Lampent in the discard pile (none Prized or stuck in hand/deck) that is just 80 damage;
Darkrai survives hits from either
Joltik or
Pumpkaboo, and
Yveltal survives attacks from
Pumpkaboo. It will take another three Night Marchers in the discard pile for
Pumpkaboo to OHKO
Darkrai thanks to Resistance, or
Yveltal thanks to its slightly beefier HP score.
Joltick needs six total Night Marchers in the discard pile to OHKO
Darkrai.
It really will come down to who gets what when. Night March isn't facing an autoloss, but if either the player or the deck itself experiences a hiccup, it may as well be. For a "fun" deck that isn't too bad, is it?
Oh, and was it still using Vileplume or does the deck have to worry about cards like Switch?