Reuniclus's excellent bulk, low Speed, Magic Guard ability, and Psychic typing let it serve as a very effective Trick Room set-up Pokemon. Its excellent Special Attack, in conjunction with recoil free use of Life Orb, allow it to deal major damage to many common VGC 2011 Pokemon while retaining decent bulk. Reuniclus has a special niche in the metagame in that it can not only reliably set up Trick Room, but also abuse it well with its high Special Attack, enabling it to be a reliable pivot with very few weaknesses.
Trick Room is the basis of this set, allowing Reuniclus to outspeed almost everything on the field. Coming from a base 125 Special Attack, Psychic is Reuniclus's STAB attack, and with a Life Orb boost, will do major damage to anything that doesn't resist it. Shadow Ball and Focus Blast complement its coverage, letting it hit everything for at least neutral damage while nabbing key KOs on many common Pokemon, such as Chandelure and Hydreigon.Team Options & Additional Comments >>>
Reuniclus has access to Snatch, which can allow it to steal Imprison from Chandelure, Tailwind from Whimsicott, and so on, but it's generally not very reliable. If Reuniclus is attacked during the turn it attempts to Snatch a move when it would normally use Trick Room, it's probably going to be defeated without successfully setting up Trick Room. Reuniclus has access to both Reflect and Light Screen, but with its low Speed, it will be far less effective at setting them up compared to the likes of Sigilyph, and Reuniclus will do far more good attacking than setting up dual screens. With Magic Guard nullifying damage from sandstorm and hail, Reuniclus can run a set utilizing Trick Room, Focus Sash, and Endeavor at a low level, using a FEAR strategy. However, this strategy is ruined should Reuniclus suffer multiple hits (notably from multi-target attacks), and its pre-evolution Duosion typically performs this role better, due to its lower HP. Recover is an option to recover health while a teammate attacks, and also to avoid Sucker Punch, but Reuniclus really doesn't have the defenses to successfully utilize it in VGC.
Reuniclus can effectively use Trick and Flame Orb in conjunction with Magic Guard to attain an immunity to status, as well as the ability to burn the opponent. Reuniclus does learn Imprison as well, and while vastly overshadowed by Chandelure due to Reuniclus's much lower Speed, it can still be useful. With Psychic and Shadow Ball on a moveset with Imprison, Reuniclus can completely shut down a plethora of Pokemon that commonly set up Trick Room.
Checks and Counters
Pokemon with Sucker Punch, such as Bisharp, Zoroark, and Druddigon can threaten Reuniclus immensely with the ability to remove it from the match before it even attacks, although at full health, Reuniclus can take most Sucker Punches without being KOed. A Fighting-type Pokemon is recommended to combat this; under Trick Room, Conkeldurr's Mach Punch outspeeds the aforementioned Pokemon using Sucker Punch, and OHKOes both users of STAB Sucker Punch. Even though this set's EVs allow it to survive a few super effective attacks, Reuniclus is severely damaged by Volcarona's Bug Buzz, Hydreigon's Dark Pulse, and Chandelure's Shadow Ball, although it can OHKO the latter two with Focus Blast and Shadow Ball respectively, assuming neither hold a resist berry.
If Reuniclus is unable to set up Trick Room, it will find itself unable to attack effectively due to its poor Speed stat. Therefore, a Pokemon that can remove or disable common users of Taunt or Imprison is very useful. Whimsicott can outspeed and Taunt every other Taunt user, while a Fake Out user such as Mienshao or Scrafty can halt opposing attempts to stop Reuniclus from setting up Trick Room. Encore is also able to neuter Reuniclus; if Whimsicott is on the field as Reuniclus uses Trick Room, it can use Encore the next turn to undo Trick Room and prevent Reuniclus from attacking. Switching out can remedy this, but this gives your opponent a free turn as you switch out. Mental Herb is an option to stop Taunt and Encore, but Reuniclus loses a lot of power when using it. Generally it is not recommended.