Okay then.
Regirock from Unlisted to B Rank in Monotype Rock.
In this generation, Monotype Rock, Steel, and Ground teams have been nerfed with the end of permanent sandstorm, which Tyranitar and Hippowdon commonly supplied. This also made Pokemon with the ability to summon weather but with no other use such as Ninetales and Politoed go to PU, and even their abilities were banned there eventually. Previously, Rock Types would receive a 50% boost to their Special Defense in a Sandstorm, allowing them to stomach super-effective hits that they would normally not be able to survive without the Sandstorm. Some recovery moves and SolarBeam were hindered in the Sand, even working better for Rock. But with the 6th Generation, Sand, and all forms of weather, are no longer permanent. This has made formerly viable threats such as Gigalith, Carracosta, and Regirock plummet tier-wise. That does not mean that all is bad for one of the legendary Rock Golems.
Boasting a skyhigh Base 200 Defense and usable
Base 100 Special Defense, along with a good Base 100 Attack, it is still able to hold it's own. It has many sets that make it a viable option in any Rock Type Team, and can be a decent replacement for Mega Aggron should you choose to run Mega Diancie/Tyranitar as your Mega of choice instead. It gets an excellent support movepool of Stealth Rock, Toxic, and Thunder Wave, and even gets solid recovery with Drain Punch, an asset that many of its team mates would kill to have. An offensive set is not out of the question, as it can either run a threating
Rock Polish Set, Choice Band, Life Orb, or a Curse SleepTalker. Regirock can run a plethora of sets effectively in Monotype Wall and could be your go-to guy to absorb a never ending fury of physical attacks, whether it means surviving a Close Combat from Infernape or a High Jump Kick from Mega Lopunny. The first set here is the Support Set:
Regirock@Rocky Helmet/Leftovers
EVs: 252 HP, 44 Attack, 16 Defense, 196 Special Defense
Ability: Clear Body
Nature: Impish
-Stealth Rock
-Stone Edge/Superpower/Rock Slide/Bulldoze
-Thunder Wave/Toxic
-Drain Punch/Fire Punch/Earthquake/Rest
The standard set for NU Regirock actually functions well in Monotype. It aims to bolster both sides of Regirock's defenses while also maintaining a supportive outlook. Should you choose to use Regirock as your lead,
Stealth Rock should always be first priority. Regirock's natural bulk allows it to set up fully before dying. With
Clear Body you no longer have to worry about Intimidate Leads because they will not be able to penetrate your defenses. If the opponent lead is setting up through Dragon Dance, Rock Polish, Double Dance, etc.
Bulldoze & Thunder Wave completely mess up your opponent. No Pokemon wants to be at -1 or at half speed, and this is a godsend to Monotype Rock as the few Rock Types with Thunder Wave are usually offensive. If you are wanting to stall,
Toxic always helps on giving the opponent a slow death.
Stone Edge is the recommended attack of choice as it gets STAB and a very high critical hit ratio, even with little investment, though you are always free to use
Superpower to dent Mega Lopunny, Chansey, Empoleon, and others. Regirock gets recovery in the forms of
Drain Punch & Rest, one doing damage while the other one acting as a Full Restore.
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In Monotype Rock, if you are running a recommended Sand Team and the Sand wares off and Tyranitar is dead, it is helpful to remember the high possibility of an offensive Regirock in the form of an all-out attacker in an
Assault Vest. Assault Vest limits Regirock to only using attacking moves, but it is noted that Regirock can still function even if being Taunted. Here comes the Assault Vest Regirock set:
Regirock@Assault Vest
EVs: 240 HP, 252 Attack, 16 Def/Spd/Sp.Def
Ability: Clear Body
Nature: Adamant
-Fire Punch/Drain Punch
-Stone Edge/Rock Slide
-Superpower/Drain Punch
-Earthquake
Assault Vest Regirock is a commonly overlooked set that can be very dangerous in the right situation. With an Assault Vest, it becomes an absurdly-bulky physical attacker nightmare that can sweep and switch into Intimidate. If Grass Types are giving you trouble,
Fire Punch 3HKO-2HKOs them, even scoring for a chance to get a burn, which severely hinders Grass Physical Attackers that could really threaten Mono Rock such as Breloom, Virizion, and physical Mega Venusaur. As mentioned before,
Drain Punch deals heavy damage to Steel Types such as Heatran but usually won't deal much, but has recovery. Another option is
Power-Up Punch if you intend to use a stalling foe as setup fodder, but will not be dealing much damage, even at +1.
Stone Edge is hard-hitting with STAB and a high critical-hit ratio, but if you are more concerned about accuracy,
Rock Slide and even
Smack Down are other options with higher accuracy at the cost of power.
Earthquake is always a good option.
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In conclusion, Regirock is a powerful asset to any Monotype Rock team. It isn't perfect, as it is another physical attacker preyed on by
Mega Sableye, but it has its uses and perks. It is generally inferior to Mega Aggron but can be a perfect substitute if the Rock T-Rex is not your Mega. It also needs significant support from Tyranitar and others to function well, but all and all, it is a very viable Pokemon that can help you wage war on Monotype Rock.