Pokemon Violet - 7* Swampert the Unrivaled with Galarian Slowking

Tera poison Swampert's water/ground/poison STAB is pretty good coverage - in fact, nothing resists all three! - but luckily they merely decided to make Swampert's setup mildly annoying instead of actually difficult.
Swampert's regular moveset is Earthquake (physical, 100 BP), Liquidation (physical, 85 BP, 20% chance for -1 Def), Hydro Pump (special, 110 BP but 80% accurate), and Sludge Wave (special, 95 BP, 20% chance to poison). It's a mixed set! Since it has both physical and special water moves you definitely want to resist water; then if you're physically-bulky you should aim to resist water too, whereas if you're specially-bulky you should aim to resist ground instead.
Tera poison Swampert is Relaxed (+Def, -Spe) and has x30 HP in a 500-second raid; it immediately uses Muddy Water (85% accuracy, 30% chance for -1 accuracy), so you might as well reset if you get debuffed; then at 90% time remaining it steals a tera charge, and at 80% time remaining it wipes player buffs and puts up shield (or at 85% HP remaining) covering 45% of its health bar, while at 60% time remaining it uses Yawn; meanwhile, at 75% HP remaining it wipes its own debuffs, and at 40% HP remaining it uses Muddy Water again. Finally, once below 50% max HP it starts acting a second time per turn 50% of the time.
Pretty weird set of extra actions! An early time-based player buff wipe plus an HP-based debuff wipe, only one each total, means you're basically free to buff and debuff as you like... which is certainly appreciated, since having to guard against a mixed set is kinda awkward.
Luckily, that means a lot of AI allies are useful! Intimidate allies are obviously handy here (especially Arcanine, who's weak to ground and water and will therefore reapply the debuff more often), Bellibolt's Light Screen can lower special damage, Gardevoir's Life Dew can help heal... but most interestingly, on top of Arboliva's Safeguard to block poison and grassy terrain to slowly regen, grassy terrain also halves Earthquake damage!
Upon seeing the news of tera poison Swampert people immediately thought of Stored Power Slowbro (myself included!), though I was gonna try Slowking first since Intimidate allies are easier to get... but as soon as I learned that the shield actually goes up at 80% time at the same time as the player buff wipe (unlike what Serebii currently says, which is that the shield goes up at 50% time remaining), I decided to pivot to Galarian Slowking instead, since it can Acid Spray through shield while also building up tera charge.
After a failed attempt (due to a crit...) where I learned that I could survive around five turns just through grassy terrain regen, I decided to swap out a Life Orb for a Weakness Policy: the +2 Atk and SpA means I can skip out on one Nasty Plot and one extra buff (like Amnesia), meaning I could possibly delay or even win entirely before needing to actually heal. As it turns out, a life cheer was indeed needed (right when terrain ran out)... but doing Nasty Plot x2, Acid Spray x3, life cheer, then tera psychic Stored Power led to a clean oneshot, as long as I wasn't crit earlier and also rolled enough life cheer healing.
...I realized afterwards that, since I'm not using a second buff move like Amnesia, I could've just slotted in Slack Off instead. Oops! Also, since terastallizing removes your ground weakness, you might as well do 3x Acid Spray first, then terastallize on your first Nasty Plot... though that does mean you need to gamble on Liquidation defense debuffs instead. Maybe a Grassy Seed (for free +1 Def) would be a safer alternative that still allows for a oneshot without a second buff move, too?
Since you can completely ignore the only debuff wipe if you skip from over-75% to dead, this raid is probably trivialized by debuffs! At least one Intimidate ally plus a Pokemon that can use Mystical Fire/Skitter Smack/Snarl/Struggle Bug (which both debuffs special attack while also building up tera charge), and you're then free to buff/debuff for the oneshot without worry of fainting. Realistically, if you still wanted to Stored Power, I'd just recommend regular Slowking, with Stored Power, Calm Mind, Iron Defense... and iunno, Chilling Water or Slack Off.
Overall, it's an interesting raid! Not really that hard, but no super-annoying tricks either. Nice to have a break from all the trickier ones.