very interested to see how this metagame progresses, cool concept. wanna give some of my initial thoughts
- Wherever possible, types should be broadcasted. For a metagame that is still in its infancy, knowledge checks can't be largely assumed; Heatran will probably be Tera Ground to avoid the 4x weakness, but it could also very reasonably be Tera Water or something too. This may just be a problem we have to deal with until games get played and we figure out what is and isn't good, but not knowing the actual type of Toxic Spikes or Stealth Rocks seems very annoying. I do agree that, at the very least, the type should be broadcasted for weathers and terrains.
- Snow and Sand seem extremely good, especially with, as drampa mentioned, the Slowkings being able to slow pivot into any breaker or sweeper and give them a big chunky Defense boost basically for free. Not sure how big of a problem this will end up being until we actually get games played, but I think that Chilly Reception is worth keeping an eye on in the early stages. Tyranitar and Hippowdon will likely have similar support potential but the lack of any pivoting moves will probably make them much less constraining.
- Curious as to how Ground-type Grassy Terrain would interact with itself seeing as Grassy Terrain is hard coded to reduce the power of Earthquake. If I'm not mistaken Earthquake would actually suffer a 20% power cut? This hypothetical probably doesn't happen anyway but still interesting to think about.
- On the topic of terrain, Misty Terrain seems good since the only type mentioned by name in the effects is Dragon, which it cuts the power of by 50%. Could have useful applications for fatter team structures in the same way Sun or Rain might.
and now some theorymons

Primarina @ Assault Vest
Ability: Liquid Voice
Tera Type: Fire
EVs: 80 HP / 252 SpA / 176 Spe
Modest Nature
- Surf
- Moonblast
- Flip Turn
- Hyper Voice
90 BP coverage of any type you want! Works with Sparkling Aria/PsyNoise too.

Kyurem @ Choice Specs
Ability: Pressure
Tera Type: Steel
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Ice Beam
- Freeze-Dry
- Draco Meteor
- Earth Power
Steels can't switch into this anymore, good luck have fun.

Garganacl @ Leftovers
Ability: Purifying Salt
Tera Type: Fairy
EVs: 252 HP / 52 Def / 204 SpD
Careful Nature
- Stealth Rock
- Salt Cure
- Recover
- Protect
Takes half damage period from any type of your choice AND chunks it to death faster with Salt Cure, will have some very unique applications in shoring up shitty matchups. (No, it doesn't stack, Water/Steel types don't take 50% from Salt Cure vanilla, thank god.)
- Wherever possible, types should be broadcasted. For a metagame that is still in its infancy, knowledge checks can't be largely assumed; Heatran will probably be Tera Ground to avoid the 4x weakness, but it could also very reasonably be Tera Water or something too. This may just be a problem we have to deal with until games get played and we figure out what is and isn't good, but not knowing the actual type of Toxic Spikes or Stealth Rocks seems very annoying. I do agree that, at the very least, the type should be broadcasted for weathers and terrains.
The sunlight turned harsh!
Pointed stones float in the air around the opposing team!
Grass grew to cover the battlefield!

Pointed stones float in the air around the opposing team!

Grass grew to cover the battlefield!

- Snow and Sand seem extremely good, especially with, as drampa mentioned, the Slowkings being able to slow pivot into any breaker or sweeper and give them a big chunky Defense boost basically for free. Not sure how big of a problem this will end up being until we actually get games played, but I think that Chilly Reception is worth keeping an eye on in the early stages. Tyranitar and Hippowdon will likely have similar support potential but the lack of any pivoting moves will probably make them much less constraining.
- Curious as to how Ground-type Grassy Terrain would interact with itself seeing as Grassy Terrain is hard coded to reduce the power of Earthquake. If I'm not mistaken Earthquake would actually suffer a 20% power cut? This hypothetical probably doesn't happen anyway but still interesting to think about.
- On the topic of terrain, Misty Terrain seems good since the only type mentioned by name in the effects is Dragon, which it cuts the power of by 50%. Could have useful applications for fatter team structures in the same way Sun or Rain might.
and now some theorymons

Primarina @ Assault Vest
Ability: Liquid Voice
Tera Type: Fire
EVs: 80 HP / 252 SpA / 176 Spe
Modest Nature
- Surf
- Moonblast
- Flip Turn
- Hyper Voice
90 BP coverage of any type you want! Works with Sparkling Aria/PsyNoise too.

Kyurem @ Choice Specs
Ability: Pressure
Tera Type: Steel
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Ice Beam
- Freeze-Dry
- Draco Meteor
- Earth Power
Steels can't switch into this anymore, good luck have fun.

Garganacl @ Leftovers
Ability: Purifying Salt
Tera Type: Fairy
EVs: 252 HP / 52 Def / 204 SpD
Careful Nature
- Stealth Rock
- Salt Cure
- Recover
- Protect
Takes half damage period from any type of your choice AND chunks it to death faster with Salt Cure, will have some very unique applications in shoring up shitty matchups. (No, it doesn't stack, Water/Steel types don't take 50% from Salt Cure vanilla, thank god.)