Seeing as though the time with DPP AG as an RoA Spotlight ladder is coming to an end shortly, I wanted to take some time to go over some metagame threats and very viable Pokémon as I saw them throughout the month of laddering and also playing in the DPP AG Tournament that Kris has been hosting for RoA!
Major Metagame Pokémon
Arceus-Normal, EKiller as it's commonly referred to in AG, is definitely a top metagame thread in DPP AG. There have been a few players running mono-EKiller teams on the ladder, which have been effective with a variety of coverage options (such as Overheat on at least one for Pokémon like Skarmory that can normally counter EKiller with its Swords Dance, Extreme Speed, Shadow Claw kind of set). Additionally, with Farceus EV restrictions not being enforced for DPP AG (unlike DPP Ubers), it certainly makes EKiller a frightening offensive weapon.
Dialga is another Pokémon in DPP AG with excellent offensive capabilities in this metagame. With its access in DPP to Adamant Orb, which boosts its Steel- and Dragon-type attacks by 1.2x, in addition to its impressive SpA stat, Dialga is a fearsome threat to most teams in the metagame. In addition, with Steel typing resisting Dark-type attacks, this makes its normally helpful Steel/Dragon dual typing even more effective.
The terror of ORAS AG as it turns out also has quite the fearsome presence in DPP AG. The combination of an 80% accuracy Sleep-inducing move that nothing can resist (no Magic Bounce as an ability in DPP, though Magic Coat can bounce it back) with its ability, which damages Pokémon with 1/8 of their health every turn they're asleep is frightening indeed. Although Darkrai does have to contend with Steel types resisting Dark-type moves as mentioned above in DPP, this can be remedied by Nasty Plot or additional coverage like Focus Blast.
Kyogre is another massive offensive threat in DPP AG. Weather is permanent in DPP, so having a weather-inducing ability such as Kyogre's Drizzle is quite potent. In addition, with access to Calm Mind, Kyogre is a threat that can rip through many teams without proper checks to it. The other nice perk of Kyogre is its ability to run an item, which can consist of Lum Berry, Leftovers, Life Orb, etc.
Additional Viable Pokémon
I thought I'd make this section to cover a few Pokémon that I've enjoyed using/have found really viable!
Forretress has been one of my favorite Pokémon to use in DPP AG. Its hazard-setting movepool is unmatched in the metagame. Access to Stealth Rock, Spikes, and Toxic Spikes make it a superb lead hazard-setter. Additionally, Forretress has fantastic bulk, and its movepool again proves very helpful here with access to Pain Split and Toxic. As a side-note, since Arceus formes have no means to remove hazards in DPP (since Defog in DPP removes the opposing field's hazards and not your field's), Toxic Spikes from Forretress, particularly when set up in the early game, can be very effective in chipping Arceus down consistently over the course of a battle.
Steelceus is another of my favorite options in DPP AG. Steel types get a nice boost in DPP as they resist Dark-type attacks. This helps make Calm Mind Steelceus a bit threat to Darkrai if a Dark Void misses. Steelceus is also very helpful as it resists Extreme Speed from EKiller and can retaliate with a powerful Judgement. I've had good success with Calm Mind, Judgement, Fire Blast, and Recover.
Giratina Origin is a cool Pokémon in DPP AG, particularly due to the combination of its solid bulk; SpA/Atk stats in its Ghost- and Dragon-type moves, which are boosted by Griseous Orb; and its ability, Levitate. Access to Will-O-Wisp is very helpful to fend off powerful physical attackers like EKiller. And Draco Meteor very few Pokémon in the meta want to/are able to tank.