Mamoswine is not too common but it can be used. Mamoswine seems like it could be pretty good due to its resistance to grass and access to priority however it does have disappointing bulk (even with an Assault Vest Mega Gengar OHKOs) that makes it 2HKOed by most common Pokemon. Its other resistances are not especially common in Inverse but it does only have one weakness. The best thing about it is being a Serperior counter.
A decent check to Glalie might be Snorlax (as long as it can dodge a Sheer Cold), as it resists Frost Breath, has high SpDef, and can hit Glalie with a STAB Chip Away regardless of how many evasion/defense boosts it has.
To the people who play this format: How exactly do you guys teambuild for it (like the full process of picking a functioning team)? Is it similar to Battle Spot Singles? I've just been struggling to make even a decent team and I want to play it before it ends.
I teambuild similarly for Inverse as I do for BSS, trying to have checks and counters to all the common Pokemon and the most powerful attacking types (Grass and Normal) with good defensive and offensive synergy. One thing is you need at least 2 checks to Mega Kangaskhan and Serperior since they are so dominating. You also need to be more prepared for Moody Glalie and Minimize.
I team build by trying to "counter" what I see. I don't make really good teams by any means but it works well xD
Then after I see enough high ranking opponents and I finally see a team that inspires me to use it almost exact as possible, I do that! At the bare minimum, the high ranking opponents' teams and move/item options help provide deeper insight!
Sitting at 1764 and #81 global atm if i was USA region demantoid would be number 2 gehehe xP
With the season almost ending and a high probability I won't play with it anymore here is the team I used for almost the whole season. Record was 33-11 with a rating of 1747.
Edit: I played some to try to get back to number 1 but I dc'ed a lot.
Sceptile was the only Pokemon I bred specifically for this format (I have become less lazy and have already bred around 5 Pokemon for the next season). I had been meaning to do so for a while and with grass being such a good offensive typing I wanted to use it this season. My other mega was Alakazam beacause I guess I wanted fast frail megas. Protect was on both to avoid Fake Out from mega Kangaskhan. Timid was chosen on mega Alakazam because it was what I had, but it proved very useful for outspeeding other Alakazams and +1 Blaziken.
Tyranitar was originally chosen to be a grass type resist, but after Diggersby joined the team I rarely ever used it(maybe once) and was a pretty useless team slot. i would probably replace it either with a scarf PorygonZ or a Suicune.
Porygon2 was chosen as a physical wall that could take many hits and spread paralysis. Thunderbolt was chosen to hit grass types super effectively. T-wave was used a lot and was very helpful speed control (it also had a habit of fully paralyzing mega Kangaskhan multiple times in a row).
Garchomp was a reliable pokemon that i brought fairly often. Rocky Helmet was chosen because i hate Kangaskhan. The only time I ever really used Swords Dance was on a predicted protect from Glalies so I could ohko next turn unless they got lucky.
The original team had a Life Orb Latios instead of the Diggersby. I replaced Latios because my team was having trouble taking down bulky Pokemon like Suicune, Porygon2, and Cresselia and I already had another psychic type on the team. Removing Latios did take away my only reliable Garchomp check and as a result i struggled to beat chomp thoughout the rest of the season. Diggersby did become the MVP of my team often sweeping teams once Kangaskhan went down or tearing holes in defensive pokemon so my megas could clean up the rest.
Ability: Rough Skin
EV: 252Atk/252 Speed
Poison Jab for opposing Garchomps. Originally it was holding Life Orb, but I changed it to Lum berry because paralysis and burn were very common. It also cures confusion from outrage.
Ability: Storm Drain
EV: 252 HP/ 252 Def
My answer to Serperior. Also, it can deal very well with other water types, because it's not weak to water/ice.
EV: 252 HP/ 252 Def
Thunderbolt for Garchomp. Foul Play was fun, I managed to KO a DD Tyranitar thanks to it. In retrospect I think that I could have changed Tri Attack or Foul Play to Toxic.
EV: 252 HP/ 252 Def
My answer to Kangaskhan.
A pretty standard team. Kangaskhan, Serperior and Garchomp were sweepers, capable of dealing with 2-3 pokemon when not stopped. Avalugg, Porygon2 and Gastrodon were meant to counter specific threats.
I really enjoyed this format, and I hope it's going to be used again in the future, this time as a double battle.