Clefable @ Leftovers
Ability: Magic Guard
EVs: 252 HP / 252 Def / 4 SpA
Bold Nature
- Calm Mind
- Moonblast
- Soft-Boiled
- Thunder Wave
Garchomp @ Rocky Helmet
Ability: Rough Skin
EVs: 240 HP / 176 Def / 92 Spe
Impish Nature
- Stealth Rock
- Earthquake
- Dragon Tail
- Toxic
We all know how dangerous CM Clef is, and it's an annoying Pokemon for this team. With a Bold nature and max defense, it's able to 1v1 four members of this team: Latios, Lando-T, Mew, and Mega Gyara. Latios can only manage 37.8 - 44.9% with Psyshock and is easily paralyzed and boosted on by Clef. Because Lando-T is defensive, EQ is only doing 32.9 - 39%. As such, Clef will win 1v1 between healing, boosting, and attacking. Mew is completely walled and boosted on, only managing a meager 25.3 - 29.9% with one of its special attacking moves. Mega Gyara is paralyzed and taken down in two hits by Moonblast. Clef also tanks a +1 Waterfall decently (49.7 - 58.8%) and can try to fish for paralysis while healing off damage with Soft-Boiled.
Jira and Coba are the two Pokemon this team relies on to deal with Clef. Although they fear switching in directly because of paralysis and taking a good chunk from Moonblast in Coba's case (39.9 - 47.3%), having something to help deal with them is nice. This is why Chomp is here. Should Jira and Coba try attacking Clef, they will have to deal with the possibility of Chomp switching in and chipping them down with recoil. This is very bad news, mainly because Jira and Coba need to avoid taking too much damage to prevent Clef from becoming too threatening. Even if Cobalion tries to suicide itself to wear Chomp down with a +2 CC, it's only doing 58.2 - 68.5% before dying to EQ. This leaves Garchomp with enough health to still annoy Jirachi with recoil after Cobalion dies.
Aside from helping with Jira and Coba, Chomp provides a secondary check to Mega Gyara alongside Clef. It's also able to poison Lando-T, making it easier for Clef to take down. Clef is probably the best Pokemon in OU when it comes to outlasting its checks and counters. With Chomp's support and Clef's ability to threaten so much of the team, sweeping here is a very realistic possibility in the long term. Try to avoid spamming Thunder Wave too recklessly, as being Synchronized by a Mew switch in leaves you more vulnerable to being lucked in 1v1 situations. Play smart and this core will perform nicely.