Cores in SM OU

Even though this core is very simple, that doesn't stop it from being a very common defensive core in the SM OU tier. This core is mostly based around type synergy that allows them to check Pokémon for each other; Toxapex can check Pokémon like Ash-Greninja, Volcarona, Mega Charizard X, and Knock Off Mega Scizor for Celesteela, while Celesteela deals with Psychic-types like Mega Alakazam and Tapu Lele in return, which are the main Pokémon that you will often see take advantage of Toxapex. Additionally, Celesteela also deals with Ground-types like Landorus-T, Garchomp, and Gliscor.

The core obviously isn't perfect, with it being notably weak to Tapu Koko. Because of this, you should make sure to pair this core with bulky Grass-types like Ferrothorn, Tapu Bulu, Tangrowth, and Amoonguss, which are some of the best checks to it. Additionally, you should also make sure to account for Heatran, Kyurem-B, Mega Mawile, and Mega Medicham. This can be done with Pokémon like Garchomp, Reuniclus, and Heatran.

Similarly to the core above, Ferrothorn + Clefable is based around type synergy. Notably, Clefable sports a resistance to Fighting and Dark, allowing it to check Fighting-type Pokémon like Mega Medicham, Hawlucha, and Mega Lopunny as well as take advantage of Choice-locked Ash-Greninja, ultimately forming a very solid core to check Ash-Greninja when combined with Ferrothorn. In addition, they form a very solid defensive hazard stacking core together, being generally hard to overwhelm for many Pokémon.

This core is quite susceptible to Pokémon like Heatran, Mega Mawile, and Magearna, so having strong checks to these Pokémon is very important. Pokémon to consider for this role include Mega Alakazam and your own Heatran. Speaking of Mega Alakazam, it fits especially nice on these type of teams, as it can force a lot of switches and make maximum use of Spikes.

Throughout recent months, Mega Alakazam + Magearna has been a consistently threatening core at high-level play. While Magearna is absurdly strong on its own, its combination of Fleur Cannon + Focus Blast is completely walled by Toxapex, meaning that it is ineffective against balance teams that use Toxapex. This is where Mega Alakazam comes in, as it has a very easy time against these types of teams. In addition, it and Magearna can overwhelm Steel-types like Ferrothorn and Celesteela that have a tough time checking the combination of the two. Finally, Mega Alakazam also checks Heatran, which is one of the main issues for Magearna.

This core fits especially well on offensive teams with Spikes support from the likes of Greninja and Ash-Greninja, because Mega Alakazam and Magearna can force a lot of switches and maximize Spikes damage. Additionally, it's important to have consistent answers such as Toxapex and Celesteela for Pokémon like Ash-Greninja and opposing Mega Alakazam, because this Magearna can't consistently check them.

This is one of the most common VoltTurn cores on bulky offensive and balanced teams, capable of supporting many threatening wallbreakers like Mega Mawile and Garchomp and sporting outstanding type synergy. Notably, Rotom-W struggles with Grass-types, which Tornadus-T can handle, and in return is able to check Heatran.

Mega Mawile + Ash-Greninja has been one of the most consistently threatening offensive cores in the OU metagame for a while. They both fit on a variety of teams thanks to their individual offensive potential and offer each other utility as well. Mega Mawile is notorious for taking advantage of bulky Grass-types that bother Ash-Greninja while also being able to pressure Toxapex a lot. Furthermore, it takes advantage of Ash-Greninja's potential as a Spikes setter really well because it forces an absurd number of switches, and Spikes also puts checks like Heatran, Greninja, and Tapu Koko into range of +2 Sucker Punch.

Generally speaking, Mega Mawile and Ash-Greninja struggle to consistently switch into play due to their frailty. Because of this, it is a wise idea to pair them up with pivots like the above core of Rotom-W and Tornadus-T.

Similarly to Mega Alakazam + Magearna, this core seeks to wear down Steel-types like Ferrothorn, Celesteela, and Magearna. However, in this core, this is done through Greninja, which is very customizable and thus will often leave the opponent guessing what moveset it is using. Similarly, Greninja also struggles to break through Toxapex, which Mega Alakazam easily takes advantage of. Another notable thing is Greninja's access to Spikes, which as mentioned before massively benefits Mega Alakazam because of its potential to force a lot of switches.

Generally speaking, you want to back this core up with a good defensive backbone like Toxapex and Celesteela to make up for the core's frailness. Alternatively, you could take a much more offensive approach by pairing them with pivots like Magearna and Landorus-T.

Tapu Bulu + Heatran has been a popular core ever since the inception of USM, as they have notable synergy; they're often used as the start of a Fire / Water / Grass core. Tapu Bulu is a solid check to Ground-types like Garchomp and Gliscor, which will threaten Heatran. Furthermore, it provides a good answer to Water- and Electric-types like Ash-Greninja and Tapu Koko, which Heatran also struggles to deal with on a consistent basis. In return, Heatran consistently pressures Steel- and Flying-types like Mega Scizor, Celesteela, and Tornadus-T, massively relieving pressure off Tapu Bulu.

As mentioned before, this core is often the start of a Fire / Water / Grass core, so consider bulky Water-types like Toxapex and Rotom-W. Additionally, you should be extremely wary of Pokémon like opposing Heatran, Flyinium Z Landorus-T, and Volcarona, which can pose massive problems for a team utilizing this core. Tapu Bulu also isn't a reliable check to Fighting-types like Mega Medicham and Mega Lopunny, so having a Pokémon that can provide this, like Reuniclus, is important.

Another core featuring Tapu Bulu! This time, however, it focuses more on its offensive potential. Tapu Bulu + Kartana is a Grass spam core that has been around for a while, as both Tapu Bulu and Kartana are incredibly hard to switch into when backed up by Grassy Terrain. Not only that, but Tapu Bulu also tends to weaken a bunch of Pokémon that can stand in Kartana's way, like Heatran, Tornadus-T, Zapdos, and Celesteela, ultimately allowing it to clean up much more easily.

Considering the frailty of this core, it's important to back them up with strong defensive cores, like Celesteela + Toxapex, which check a wide variety of Pokémon. Additionally, it's incredibly important to have a Heatran check like Garchomp, as Tapu Bulu and Kartana can't consistently deal with it.