Nihilego is capable of decimation and tanking to a respectable extent. Its advantage lies in its Rock / Poison typing, which is offensively good against two major forces in the 1v1 metagame&mdashKyurem-B and Charizard. This combined with a Speed stat that just outspeeds them makes it a decent counter to those two Pokemon. Its formidable special bulk allows it to tank strong moves like a Hydro Pump from Keldeo with ease. Also, while it might seem to have a moderate base 127 Special Attack in a metagame inclined towards total decimation or ridiculous stalling, Z-Moves help Nihilego in countering Rock-, Ice-, and Fire-type Pokemon if Continental Crush is used or Grass- and Fairy-type Pokemon if Acid Downpour is used. Although it has a base Defense of 47, it is physically not too frail and can tank Kyurem-B's STAB Outrage with investment in Defense. Thus, Nihilego's capabilities lie in it being both a fast sweeper and a fairly bulky sweeper as well. Having said this, its bulk is just not enough to tank super effective physical moves, and its 4x weakness, Ground, is largely made up of physically based Pokemon. Also, Nihilego’s typing means that it is weak to Steel- and Ground-type Pokemon, which it can't KO due to lack of coverage. Its low Defense stat also means that it is not able to completely wall all physical Pokemon faster than it like Earthquake Mega Pinsir, Durant, and Terrakion.
Nihilego @ Rockium Z
Ability: Beast Boost
EVs: 128 HP / 248 Def / 132 SpA
- Acid Spray
- Sludge Wave
- Power Gem
Acid Spray can be used to weaken opposing bulky Pokemon like Calm Mind Mega Slowbro, Calm Mind Mega Sableye, and Stockpile Toxapex while not having to worry about being Taunted because it deals damage as well. Substitute blocks Thunder Wave, Mirror Coat, and sleep-inducing moves, since Nihilego could be the target for Spore and Yawn users. It also helps in tanking random, possibly fatal, Z-Moves it might encounter in totally clueless matchups. Power Gem helps in defeating Kyurem-B, Mega Charizard Y, and Mega Charizard X and, by extension, other Fire-, Ice-, and Bug-type Pokemon. Sludge Wave is helpful against Fairy-type Pokemon, like the Guardian Deities.
The EVs allow Nihilego to tank a maximum-Attack Mega Charizard X Outrage, and the rest of the EVs go into the Special Attack to allow Nihilego to take out full-HP moderately bulky Kyurem-B with Continental Crush. Rockium Z converts Power Gem into a strong 160-Base Power Continental Crush, which is required to take out Kyurem-B and Charizard.
Nihilego's Rock / Poison typing means it can be sent against Fire-, Ice-, Bug-, and Fairy-type Pokemon, since Nihilego has an edge over them. Since its primary targets are stall Pokemon, the best course of action would be to use Substitute followed by Acid Spray and then finishing with Continental Crush or Acid Downpour, depending on the type. Try to avoid sending it in against Steel-type Pokemon, because Nihilego has nothing to use against them. Since some Mega Charizard X variants might carry Earthquake, this must be kept in mind before choosing a Nihilego versus a Mega Charizard X.
Nihilego's low Defense and weakness to Ground make Ice-type Pokemon like Avalugg and Kyurem-B, which have considerable physical bulk, fit in very well with Nihilego. Nihilego's typing and inability to handle Steel- and Ground-type Pokemon make it a near necessity to have a counter to these Pokemon, like Mega Gyarados or Mega Blastoise, and these go well with each other, considering Nihilego takes care of their Grass weakness. Since Nihilego is weak to Water-types, Grass-type Pokemon like Kartana and Mega Sceptile could be used to counter Water-types. In this context, Kartana is much more relevant and more useful, since it could run Sacred Sword to counter Dark-type Pokemon. Also, Nihilego's weakness to Psychic- and Steel-type Pokemon makes Volcarona a viable teammate for Nihilego to cover its Psychic and Steel weaknesses against Pokemon like Mega Metagross and Mega Lucario. Fast Mega Heracross is also a good teammate for Nihilego, since the latter is weak to Sturdy Pokemon, Jumpluff, Heatran, and Mega Gyarados, which Mega Heracross covers, and also since Nihilego covers Mega Heracross's Fairy and Rock weaknesses.
Since Nihilego has a good Speed tier, it can be alternatively used as a fast Z-Move user, or the aforementioned EV set with Acid Downpour to check Fairy-types even better. A Choice Specs set with Hidden Power Fire or Ice and Dazzling Gleam instead of Substitute and Acid Spray could help it check Fighting-types and slow Ground-type Pokemon more easily. However, these sets could be countered easily by Pokemon bulky enough to take the hits, and it is significantly tougher to bulk against a Z-Move user, since it takes a lot more EVs.
Checks and Counters:
Substitute-stall Pokemon: Pokemon that utilize Substitute to stall like Toxapex can be tough to crack, since Nihilego depends on Acid Spray to get through bulky Pokemon.
Special Tanks: Meloetta and Mega Gyarados can handle Nihilego's special moves easily and return the damage in full with Psychic or Psyshock and Waterfall, respectively.
Sturdy Pokemon: Common Sturdy threats in the 1v1 metagame include Donphan, Golem, and Crustle, against which Nihilego is totally at a disadvantage since they can endure one attack from Nihilego and KO back with their own
Strong STAB hitters: Nihilego is easily cracked by Pokemon that can survive its attacks and return with strong super effective STAB attacks, like Mega Blastoise's Hydro Cannon.
Steel-type Pokemon: Steel-types like Mega Lucario, Magearna, Mega Metagross, and Ferrothorn check Nihilego because its Poison-type attacks deal no damage and Rock-type attacks are not very effective.
Ground-type Pokemon: Ground-types like Garchomp and Landorus-T also check Nihilego, since they resist both of Nihilego’s STAB attacks.