Some sets for returning mons, along with some new and modified sets for mons with returning moves post-DLC:
Mandibuzz @ Heavy-Duty Boots
Ability: Overcoat
EVs: 252 HP / 204 Def / 52 SpD
Tera Type: Poison / Fairy
- Foul Play / Knock Off
- U-turn / Toxic
- Defog
- Roost
The given spread lives a +2 Tera Water Ivy Cudgel from Ogerpon-Wellspring, and Mandibuzz appreciates the remaining investment in Sp.Def for Gholdengo; with this it lives Shadow Ball into Make it Rain even if they get the Sp.Def drop on the switch while also dodging a potential 2HKO from Dazzling Gleam. Knock Off is a good general option for a STAB move while Foul Play will OHKO a +2 Ogerpon in return, along with helping to prevent this mon being used as setup fodder. U-turn is good for momentum into Gholdengo coming in to block a Defog, while Toxic can also be used to force progress and put opposing mons on a timer. Tera Poison flips the matchup into Fairy types, though as with all defensive mons, Fairy could also be considered as a good neutral typing that assists in the Specs Dragapult matchup. These are just suggestions though and other Tera types could definitely be explored.
Rillaboom @ Terrain Extender / Eject Button
Ability: Grassy Surge
EVs: 204 HP / 252 Atk / 52 Spe
Tera Type: Fairy / Steel
Adamant Nature
- Grassy Glide
- Knock Off
- U-turn
- Drain Punch / Taunt
Rillaboom @ Choice Band
Ability: Grassy Surge
EVs: 252 Atk / 4 Def / 252 Spe
Tera Type: Grass
Adamant Nature
- Grassy Glide
- Wood Hammer
- Knock Off / Drain Punch
- U-turn
Rillaboom @ Life Orb / Miracle Seed
Ability: Grassy Surge
EVs: 204 HP / 252 Atk / 52 Spe
Tera Type: Grass
Adamant Nature
- Grassy Glide
- Knock Off
- Drain Punch
- Swords Dance
With the return of Grassy Glide, Rillaboom should always slot this into its moveset as a strong form of priority that essentially defines this mon. I'd argue that it is objectively better than Drum Beating on the listed support set and is a necessity on banded, with Hammer also being good enough that Knock or Drain Punch is the move to drop.
Additionally, while I haven't used this set myself and so cannot provide a more intricate EV spread than outspeeding any Kingambit, SD Rillaboom is something that I've seen myself on ladder and is likely much better now that it has strong priority in the form of Glide. Miracle Seed provides extra power to Glide and ensures an OHKO on Ogerpon-Wellspring with +2, while Life Orb gives more power generally at the expense of longevity. Grassy Seed with Acro could be considered, but I feel that this set has been left behind in Gen 8 and is no longer viable.
Sneasler @ Grassy Seed / Psychic Seed
Ability: Unburden
EVs: 252 Atk / 4 Def / 252 Spe
Tera Type: Flying / Dark / Ghost
Adamant Nature
- Swords Dance
- Close Combat
- Dire Claw / Gunk Shot
- Acrobatics / Lash Out / Shadow Claw
Following on from a sharp increase in Rillaboom's viability, Grassy Seed should be added as an option for Sneasler as it is by far the most common way to activate it, even pre-DLC this had much more usage than Balloon or White Herb (which is almost never used, according to Pikalytics) and is just a better set. Psychic Seed is also something worth considering, as this mon with that item is on almost any Psyspam team. I'd also argue that Tera Blast Ground is not a viable option on Sneasler as this sees no real usage due to its reliance on Tera when other moves can be ran to hit the same targets bar Pex, who is not common enough to justify it.
Tornadus-Therian @ Heavy-Duty Boots
Ability: Regenerator
EVs: 252 HP / 40 Def / 216 Spe
Tera Type: Steel / Water
Timid Nature
- Bleakwind Storm / Hurricane
- Heat Wave
- Knock Off
- U-turn
This is essentially the National Dex Tornadus-Therian set, but with Bleakwind as a preferred option over Hurricane as a more consistant STAB option and both Heat Wave and Knock Off due to Torn losing Defog. The given spread outspeeds non-booster Iron Valiant while maximising PhysDef. The NatDex Tera type of Steel has been retained here for Dragonite's Espeed and to flip the defensive matchup on Ice and Rock moves, but Water could potentially be considered for a good neutral defensive typing due to the lack of strong Electric types in OU bar Zapdos and Grass types being threatened out by its Flying STAB, although this worsens its ability to switch into and force out Ogerpon.
Garchomp @ Loaded Dice
Ability: Rough Skin
EVs: 252 Atk / 4 SpD / 252 Spe
Tera Type: Ground / Steel
Jolly Nature
- Earthquake
- Scale Shot
- Stone Edge / Iron Head
- Swords Dance
With the return of Scale Shot, SD Garchomp now can run Loaded Dice with Scale Shot to boost its speed using a strong 100-125BP STAB move. Stone Edge secures a clean OHKO even at +0 on Enamorus who walls Chomp's STAB attacks, while Iron Head requires Tera to do this but is a stronger move post-Tera that also hits Iron Valiant and gives you the benefits of Steel's resistances to Ice, Dragon and particularly Fairy. Tera Ground is likely the best option outside of a defensive tera like Poison for the Stone Edge set, as Rock is horrible defensively. Unfortunately, both sets are walled by Corviknight, but Fire Fang is no longer viable with Enamorus in the tier; Tera Blast Fire could be considered and I've seen it suggested before but I didn't think this was worth serious inclusion.
Crawdaunt @ Choice Band
Ability: Adaptability
EVs: 252 Atk / 4 SpD / 252 Spe
Tera Type: Water / Dark
Adamant Nature
- Crabhammer
- Knock Off
- Aqua Jet
- Close Combat / Crunch
Crawdaunt @ Life Orb / Mystic Water
Ability: Adaptability
EVs: 252 Atk / 4 SpD / 252 Spe
Tera Type: Water
Adamant Nature
- Crabhammer
- Knock Off
- Aqua Jet
- Swords Dance
Unfortunately, Mr. Craw has been struggling to find a good place in OU post-DLC despite the tier being full of bulky Ground types like Gliscor and Great Tusk that this mon would typically enjoy the presence of, further contributed to by Adaptability's negative interaction with Tera. However, I do believe it still has a place as a breaker, and many teams (particularly stall) still fall apart to a well-played Crawdaunt.
The banded set is the same as it always has been, with Close Combat to hit Kingambit and Crunch as an alternative to help break through bulky waters like Dondozo, Alomomola and Toxapex after they've earlier taken a Knock Off. SD Crawdaunt is another viable option, with either Life Orb or Mystic Water as power-boosting items. Either Tera Water or Dark can be used on the banded set but they should only be clicked if a small boost is necessary to kill a mon, since this removes your Adaptability bonus on the other type and only gives a small power increase. Similarly, the SD set should not use Tera unless absolutely necessary, and this will likely only be relevant if the 12.5% boost is needed for Aqua Jet to prevent revenge killing.