Pure Evil

¡Only Dark Energy!

The strat is simple: 

1. Get Hypno on the Bench and Weezing (with 1 dark energy) on the Active Spot.
2. Use Hypno's ability and attack with Weezing.
3. Let Darkrai EX accumulate energies on the Bench and/or give Weezing a Rocky Helmet for extra chip damage.
4. Enjoy dealing 50-90 damage per turn plus having a 62.5%-75% chance to avoid damage on your turn, every turn (once set up).

Extra tips:

• Use the Red Card to prevent the opponent from setting up.
• Avoid putting Drowzee or Hypno on the Active Spot at all costs. If it ends up there you'll most likely have to sacrifice it and set up another one on the Bench.
• If Weezing is low on HP, use Koga to fully heal it for free. Ideally, have a benched Weezing prepared to immediately put in the Active Spot. Then place the Koffing you just got back on the open Bench spot.
• If your Darkrai EX can take out the opponent's Active Pokémon, you can use Koga to switch and surprise your opponent.
• If you struggle to set up, rely on Darkrai EX.

Variations:

• You can switch Rocky Helmet for Sabrina/Mars/Blue/Giant Cape for a more defensive game plan.
• You can switch Red Card for Cyrus/Giovanni/Dawn/Leaf/X Speed for a more aggressive game plan.
• I can see Sneasel>Weavile EX synergizing with Darkrai EX and Cyrus, but there are better decks for that.
• I've considered switching Red Card and Rocky Helmet for Mew EX and Budding Expeditioner, that way you have extra survivability and an answer to powerful set-ups. Not sure it would work though.
• Before Darkrai EX I used to have Ekans>Arbok, which kinda works too.
• Murkrow>Honchkrow for extra damage, maybe?
• Feel free to experiment and create your own combos :3