I considered making a Scarf Darkrai offensive, but figured most people would be making an offense with rai, so I went with a balance.
Since Dark Void is no longer viable, and Hypnosis will never hit for me, I went with a Nasty Plot, 3 attack variant.
Poison + Electric coverage allows it to take care of Ho-oh, Yveltal, Waterceus, and Primal Kyogre, while still being able to keep Fairies in check.
I wanted to pair it with the infamous support Groundceus.
This gave me a check/switch-in to Primal Groudon, Zygarde, and Steels, as well as giving me a defogger in the process.
Lugia was added to keep physical attackers, mainly set-up sweepers, from getting out of hand.
Primal Groudon was added as the mandatory Stealth Rocker, and does what it always does.
As the fifth mon I settled on Magearna, which deals with every form of Xerneas reliably, adds a much needed Toxic immunity to the team, is a Dark type resist, and serves as a switch-in to strong special attackers like Yveltal and Primal Kyogre.
For the last member of the team I went with Mega Salamence.
I had no mega yet, and felt like it was the way to go in order to patch up the Ho-oh weakness, and add a bit more offensive presence to the team, as it would struggle to break (Chansey) stall without it.