nice meme broIt's no secret that has been terrorizing the metagame with many teams finding themselves completely incapable of switching into its Choice Specs Shadow Ball, being outrun and revenge killed by the Choice Scarf variant, or broken through by a +2 Life Orb Shadow Ball/Sludge Bomb/Focus Blast. While previous attempts to safely check these wide variety of offensive options have produced inconsistent gimmicks such as Shadow Ball today I'd like to bring attention to a reliable, consistent answer to Gengar that maintains usefulness even outside of beating Gengar
MUK
252 SpA Gengar Shadow Ball vs. 252 HP / 252+ SpD Muk: 94-112 (22.7 - 27%) -- possible 5HKO after Black Sludge recovery
252 SpA Choice Specs Gengar Shadow Ball vs. 252 HP / 252+ SpD Muk: 142-168 (34.2 - 40.5%) -- 49.5% chance to 3HKO after Black Sludge recovery +2 252 SpA Life Orb Gengar Shadow Ball vs. 252 HP / 252+ SpD Muk: 246-290 (59.4 - 70%) -- guaranteed 2HKO after Black Sludge recovery
+2 252 SpA Life Orb Gengar Shadow Ball vs. 252 HP / 16+ SpD Muk: 304-359 (73.4 - 86.7%) -- guaranteed 2HKO after Stealth Rock and Black Sludge recovery
252 SpA Choice Specs Gengar Shadow Ball vs. 252 HP / 88+ SpD Muk: 163-193 (39.3 - 46.6%) -- guaranteed 3HKO after Stealth Rock and Black Sludge recovery
4 Atk Muk Payback (100 BP) vs. 0 HP / 0 Def Gengar: 228-270 (87.3 - 103.4%) -- 18.8% chance to OHKO
12 Atk Muk Payback (100 BP) vs. 0 HP / 0 Def Gengar: 230-272 (88.1 - 104.2%) -- guaranteed OHKO after Stealth Rock
156 Atk Muk Payback (100 BP) vs. 0 HP / 0 Def Gengar: 262-310 (100.3 - 118.7%) -- guaranteed OHKO
56+ Atk Muk Payback (100 BP) vs. 0 HP / 0 Def Gengar: 264-312 (101.1 - 119.5%) -- guaranteed OHKO
252 SpA Choice Specs Gengar Shadow Ball vs. 248 HP / 188 SpD Muk: 163-193 (39.4 - 46.7%) -- guaranteed 3HKO after Stealth Rock and Black Sludge recoveryhttps://replay.pokemonshowdown.com/gen8bdspou-1499942255
https://replay.pokemonshowdown.com/gen8bdspou-1499913308-ygeopbjz4b7pvnelardzrxruhya6i47pw
https://replay.pokemonshowdown.com/gen8bdspou-1499945305-j7b56m00r4gqwz08liu98r77j5ggkefpw
https://replay.pokemonshowdown.com/gen8bdspou-1499935346-tloed7typ4wjurhjonc6xk84ldmfmxfpw
(there where 2 more but I can't find them or remember whose they where so if one of the people with those replays sees this pm me and I'll edit in them in)
Credits to: 6Roggenrolas, Lord Falinks, AstilCodex, bhkg, 1q2q, jojoreference4444, Had Sweep, and Woopre for their contributions to finding and exploring Muk
The key asset that allows Muk to serve as a legitimate answer to Gengar is its massive base 105 HP and Special Defense along with its access to Payback which has a chance to OHKO Gengar even from uninvested Muk and can be guaranteed with minimal investment and/or chip damage from Stealth Rock or Gengar's own Life Orb. With this Muk manages to reliably switch into any variant of Gengar reliably regardless of the set and pose a serious threat to Gengar in return. This is an achievement not even Calm Mind or Shadow Ball Blissey can boast but why do we care? After all a one trick pony who can only threaten 1 specific Pokémon will always be an inconsistent matchup fishing gimmick that can by no means be argued to be an answer to a potentially problematic Pokémon so what makes Muk different? Well what makes Muk different is quite simple, not only does Muk not require anywhere near maximum investment to answer Gengar allowing it a great deal of flexibility to explore its options outside of Payback but those options also allow it to both answer and threaten a large variety of common metagames staples meaning Muk can remain useful against many of Gengar's partners and teams that don't even have Gengar to begin with.
Seeing as Muks primary asset is its defensive utility we'll start there. Defensively Muk can find many switch in opportunities against common metagame threats such as any variant of Blissey, Breloom, Clefable, Gengar, Magnezone, Roserade, Rotom-Wash (so long as Muk is Sticky Hold), Scizor, Skarmory, Tangrowth, and Togekiss along with most variants of Empoleon, Jirachi, and Heatran,. While this is quite an long list of switch in opportunities that doesn't mean much if Muk can't make anything out of those opportunities. Thankfully Muk's surprisingly deep movepool and flexibility in its EV spread grant it a vast and quite unpredictable list of offensive pressuring methods to threaten the opposing team.
Offensively Muk has the obvious poison STAB in either Poison Jab or Gunk Shot which allow it the threaten the fairies that have risen in response to the potent dragon type onslaught and the bulky grasses such as Tangrowth and Roserade that rose in response to the rise of offensive waters with Poison Jab even having a synergistic combo along side the Poison Touch ability giving it an effective 51% poison rate pressuring even the neutral targets that may try to switch in. As for the coverage Muk has access to Brick Break, Power-Up-Punch, and Focus Punch to punish the steels which may believe Muk is a free switch for them with Brick Break being the reliable option and Focus Punch being more prediction reliant. However given the passivity of most steels and their assumption of safety Focus Punch can be used for a more immediate punish even if you don't call the steel on switch in. That being said not all steels fear fighting move however the only 3 OU steels that posses this quality are Scizor, Skarmory, and Jirachi with Skarmory's need to roost making it vulnerable to fighting moves and Jirachi (as well as the rare Brongzong and Metagross) being punishable by the required Payback. This leaves only Scizor as a steel safe to switch in regardless of prediction.
Or it would if it wasn't for Fire Blast Muk! Now while this seems gimmicky and unreliable Muk actually has just enough Special Attack to 2HKO maximum Special Defense Scizor even with 0 Special Attack investment and a Careful/Adamant nature while also OHKOing the rare fast Swords Dance variant if Muk runs a -Speed Nature such as Sassy, Brave, or even Quiet. Quiet may sound like an odd choice for Muk however running Quiet not only helps the power of Fire Blast but also maximizes the healing of Giga Drain which Muk can use to hit waters (primarily Rotom-Wash) for decent damage even uninvested, but more importantly aids in Muk's unfortunately lacking recovery which is otherwise limited to Rest+Sleep Talk variants or requires support from a teammate which could simply be Wish support or the Rest 3 attacks variant having an Aromatherapy or Heal Bell user or (both of which can be provided by an already excellent Pokémon in Clefable). These are all the primary options we have been able to find for Muk however Muk also possess many other utility options which others may find use for in Haze, Disable, Explosion, Memento, Taunt, and priority Shadow Sneak as well as a handful of other coverage options which will allow Muk to continue adapting to the changing metagame around it.
While that was quiet a long tangent away from Gengar it again shows the capabilities of Muk outside of simply switching into any Gengar and proves that a team using Muk to answer Gengar is not handicapping themselves with some matchup fishing gimmick but is instead utilizing the unique attributes of a truly reliable and threatening Pokémon who holds its own place in the metagame on some of the best playstyles around such as Stall, Bulky Offense, Balance, and even Hyper Offense pivoting into a Gengar seeking the revenge KO and either attacking back or using Memento to allow something like Swords Dance Lucario to safely set up an potentially sweep the opposing team.
As clear as it is that Muk has a genuine place in the metagame allowing teams to switch into Gengar without requiring something as passive and hard to fit for certain playstyles as Blissey it still remains to be seen if this newly discovered threat will be enough to stop Gengar's currently ongoing slaughter. After all Muk is by no means flawless with its awkward recovery options and inability to touch the currently #2 in usage Gliscor requiring its team to keep these limitations in mind and preventing Muk from being mindlessly slapped onto just any team. In spite of this I believe Muk is currently the best option to create a metagame where Gengar can remain in BDSP OU.