[OVERVIEW]
Reuniclus is a solid option as an offensive Trick Room setter, sporting both a Spore immunity and the ability to OHKO Amoonguss. Being capable of hitting most of the metagame neutrally, Reuniclus's powerful Psychic/ + Fighting coverage lets it shine where other passive Trick Room setters cannot, giving it the capability to take full advantage of the speed control provided by Trick Room. However, Reuniclus is also frail, leaving it vulnerable without proper support and positioning. In addition, its vulnerability to common priority attacks such as Sucker Punch and Talonflame's Brave Bird can leave it rather vulnerable (you used vulnerability earlier in this sentence, so change this to something else) to losing momentum even after setting Trick Room. It also lacks the defensive capabilities and Ground immunity offered by other options such as Cresselia. Reuniclus, and it is susceptible to being walled by Aegislash, a common Trick Room check.
[SET]
name: Offensive Trick Room Setter
move 1: Psychic
move 2: Focus Blast / Shadow Ball
move 3: Trick Room
move 4: Protect
item: Life Orb
ability: Overcoat
nature: Quiet
evs: 152 HP / 36 Def / 252 SpA / 68 SpD
ivs: 0 Atk / 0 Spe
[SET COMMENTS]
Moves
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Psychic hits is Reuniclus's main STAB, hitting most threats neutrally besides Steel- and Dark-types such as Heatran, Aegislash, Hydreigon, Jirachi, Hydreigon, and Scrafty, and it has while having a good chance to OHKO standard Amoonguss. Focus Blast lets Reuniclus hit those Steel- and Dark-types, (AC) except for Jirachi and Aegislash, (AC) for super effective damage. Shadow Ball is a good option for covering Aegislash, (RC) and also is guaranteed to break Substitutes on Steel-types such as Heatran gets guaranteed sub breaks on steels like heatran without having to risk a 30% chance to miss. Trick Room allows slower Pokemon to take advantage of the reversed move order and put the opponent on the defensive for 4 four turns. Protect is an all-around staple for Doubles Pokemon, allowing Reuniclus to avoid damage while maneuvering with its partner [does something], and it also is a good move for dodging Sucker Punch if you don't want to switch and Trick Room is already up.
Set Details
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Maximum Special Attack EVs and a Quiet nature enables Reuniclus to maximize its Reuniclus's damage. Minimizing Speed allows Reuniclus to get the valuable Speed ties with Amoonguss, KOing it before it can Spore Reuniclus's partner, and also allows allowing Reuniclus to underspeed most Pokemon things in the metagame. The distribution of the remaining EVs between HP, Special Defense, and Defense maximizes Reuniclus's bulk in the most efficient way possible, letting it survive live Aegislash's Shadow Ball and giving it an extremely high chance of surviving living Kangaskhan's Sucker Punch, though only from full health at full hp, as well as while also giving it a nice Life Orb number.
Usage Tips
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Avoid letting Reuniclus tank hits outside of Trick Room by positioning it such that your opponent can't double target Reuniclus down as it sets up Trick Room, for example by supporting it with Fake Out such as supporting Reuniclus with fake out or redirection. Take advantage of Reuniclus's strong offenses by simply attacking if you predict the opponent will Taunt Reuniclus, such as with Keldeo or Thundurus, taking out for a significant portion of their HP. When Trick Room is down not active, be conscious of whether or not you really want to set it trick room to be up; sometimes it can be better to simply attack rather than set up Trick Room, (AC) especially against slower threats such as Ferrothorn and Amoonguss or priority attackers such as Talonflame. Reuniclus is a good switch-in to on status-inflicting moves such as Spore and burns (Will-O-Wisp I assume?) and Fighting-type attacks,; (ASC) however, (AC) almost everything else hits it neutrally and chunks it too hard (lol, is something like "dents" an okay replacement for chunks? that's sort of a weird choice...or "takes a chunk out of it"), making it difficult for it to set up Trick Room.
Team Options
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Reuniclus fits well on Trick Room teams, so Trick Room setters as well as Trick Room attackers are good partners fit very well and take advantage of the speed control provided. Bulky Ghost-type setters to fill in the "one offensive, (RC) and one defensive Trick Room setter" composition, (AC) such as Jellicent or and Gourgeist, (AC) are valuable options that provide a defensive backbone, allowing the team to absorb hits that Reuniclus can't. Fake Out support from Pokemon such as Scrafty or and Hariyama, which complement Reuniclus's its typing weaknesses very well, and help your team safely set up Trick Room be set up are solid options. Redirection from in the form of Amoonguss is valuable in helping Reuniclus set up Trick Room, drawing away taking hits that Reuniclus wishes to avoid. Checks to Aegislash, Hoopa-U, and Bisharp such as Mega Camerupt and or Scrafty complement Reuniclus well and which enjoy the speed control offered by Trick Room compliment Reuniclus well. Other Trick Room attackers such as Rhyperior and Sylveon work well together with Reuniclus, (AC) as they these options benefit from Reuniclus countering Grass-types grasses such as Amoonguss very well.
[STRATEGY COMMENTS]
Other Options
=============
Reuniclus can use Focus Sash or Mental Herb if it wants to sacrifice damage for an easier time setting up Trick Room. However, Mental Herb is not usually vital for Reuniclus because it does not become dead weight offensively even after being Taunted; it , and is still able to deal heavy damage thanks to its high Special Attack stat. In addition, Life Orb is vital for Reuniclus's damage output, which drops significantly if it runs when one uses Focus Sash. Helping Hand can be useful for used when you Reuniclus forsees an incoming Fake Out, as Helping Hand has higher priority than Fake Out. For abilities, Regenerator is an interesting option that enables Reuniclus to restore its HP bulk after taking a hit, giving it good rotational power, but Overcoat's spore immunity is are incredibly valuable for a Trick Room team. Regenerator can fit on Reuniclus when it is used on semi-Trick Room Semiroom teams rather than full Trick Room Fullroom. Colbur Berry is an option that lets Reuniclus tank one Dark-type hits better.
Checks and Counters
===================
**Typing Advantage**: (colon) Reuniclus suffers against Aegislash, which resists or is immune to both Psychic and is immune to Focus Blast, whereas Jirachi redirects Reuniclus's attacks and its hits are redirected with relative ease by Jirachi. Outside of Trick Room, powerful Dark- and Ghost-type STAB attacks dark and ghost stabs such as Hoopa-U's Hyperspace Fury or and Hydreigon's Dark Pulse threaten to KO Reuniclus.
**Speed Control**: (colon) Foes Opponents carrying Trick Room, especially Cresselia, are capable of forcing Reuniclus into play mind(space)games of whether or not they opponent will attempt to reverse their its own Trick Room.
**Speed**: (colon) Priority attackers Pokemon such as Bisharp, Talonflame, and Kangaskhan are all capable of operating and being big threats even under Trick Room due to their priority attacks.
**Utility**: (colon) While Reuniclus is still able to maintain a strong offensive presence even while being Taunted, being Taunted both prevents Reuniclus from setting Trick Room and nullifies its Reuniclus' ability to defend itself with Protect. In addition, Fake Out is powerful utility versus trick room setters that aren't immune to normal such as Reuniclus, as it may gives the opponent free turns and damage, (RC) while also pressuring Reuniclus to use Protect, and leaving it vulnerable the next turn.