Camerupt-Mega @ Cameruptite
Ability: Magma Armor
EVs: 128 HP / 252 SpA / 128 Spe
Modest Nature
- Fire Blast
- Earth Power
- Rock Slide
- Stealth Rock / Substitute
Celesteela is a solid mon in the metagame, and this set utilizes its good defensive typing to be a good mixed wall, handling threats like Tapu Lele and Mega Pinsir quite well. However, it's offensive presence is a bit lackluster (sans Leech Seed and Protect shenanigans), leaving it vulnerable to common offensive threats like Tapu Koko and Heatran, and dangerous set-up sweepers like Volcarona (which is on the rise once more). Celesteela is also unable to do much to defensive mons like Toxapex, which can fish for burns and set up hazards for free, and Mega Venusaur and Mega Sableye, which are immune to Leech Seed (while Seeding Celesteela itself or Knocking Off Leftovers, which also sucks).
Mega Camerupt is a surprisingly good partner for Celesteela, as it gives a vital Electric immunity, Fire resist, and strong wallbreaking power. Celesteela absorbs random Scalds and is immune to Ground-type moves, while also setting up Leech Seed for Mega Camerupt to heal up off of. Mega Camerupt is pitifully slow and will likely take a hit as it switches in, so Leech Seed recovery is very much appreciated.
This Mega Camerupt set has enough speed to outspeed Toxapex and OHKO with Earth Power, which is pretty much the only benchmark you need to really hit. Fire Blast and Earth Power obliterate Mega Venusaur (even defensive sets), Heatran, Toxapex, Magnezone, Zapdos, Tapu Koko, and (ironically), other Celesteela, all of which are viable switch-ins to the given Celesteela set. Rock Slide kills Volcarona, and you live any +1 move as well (even the +1 Inferno Overdrive), making Mega Camerupt a hard counter to a rising threat to Celesteela. Rock Slide also hits Mega Charizard Y, which is much less common than it used to be. The last slot is mostly filler-Mega Camerupt forces out or beats common Defoggers like Zapdos, Mew, and Mega Scizor so you can likely set up Rocks several times if needed. Substitute is great for easing predictions and Mega Camerupt hits hard enough that a successful sub usually means at least one KO. Yawn and Nature Power are viable options too.