Celesteela

Celesteela has an excellent defensive typing, letting it wall Pokemon such as Xerneas, Mega Diancie, and Primal Groudon when using a Primordial Sea set. An immunity to Ground means it can function as an excellent entry hazard remover due to it only being damaged by Stealth Rock. In addition, in conjunction with Primordial Sea, Celesteela can sport simultaneous immunities to Fire- and Ground-type attacks, which are the most common coverage moves used to defeat Steel-types. It has competition from other Steel-types, such as Registeel and Ferrothorn, but has the niche of not requiring an ability to be immune to Ground. Its typing also allows it to check Kartana as well as Mega Garchomp, two Pokemon that may be difficult to defensively check otherwise.

However, while Celesteela's bulk is decent, it is not spectacular for a wall, so it finds difficulty in taking strong neutral attacks such as from Primal Kyogre and Mega Gyarados. In addition, it even struggles to take some resisted attacks such as Steelworker Kartana's Sunsteel Strike. A weakness to Electric means it does not like switching in on most specially-oriented wallbreakers, as they tend to use Volt Switch. The lack of a Rock-type resistance also means that Celesteela faces difficulty taking on Pokemon such as Mega Tyranitar and Magic Guard Mega Diancie. Celesteela is very reliant on using Primordial Sea to carve a good niche in the metagame, meaning it does not have much freedom in what it runs, as other sets are done better by the previously mentioned Steel-types. Due to its reliance on Primordial Sea, it finds difficulty in checking offensive Water-types in the tier such as Primal Kyogre, Palkia, and Ash-Greninja. While it can run Flash Fire to somewhat remedy this weakness to Water-types, Celesteela is not made to check the listed Water-types anyways, so there isn't much benefit.