Moves
Hypnosis puts a foe to sleep, allowing Xurkitree to safely set up Tail Glow and potentially avoid getting revenge killed by Focus Sash users and Mimikyu. With Psychium Z, Xurkitree can use Z-Hypnosis, which allows it to gain a Speed boost and outspeed most of the unboosted metagame. Tail Glow boosts Xurkitree's already astronomical Special Attack stat to the point where it can rip through foes that resist its moves with brute force. Thunderbolt is Xurkitree's most consistent Electric-type STAB move and deals heavy damage to neutral foes even when unboosted. The fourth move rounds out Xurkitree's coverage by hitting Ground-types. Hidden Power Ice OHKOes the most common Ground-type in Battle Spot Singles in Landorus-T, hits Thundurus-T, and disposes of Assault Vest Tapu Bulu at +3 after Stealth Rock damage. Energy Ball handles Ground-types that are not weak to Hidden Power Ice, such as Mamoswine, Excadrill, and Mega Swampert. Unlike Hidden Power Ice, boosted Energy Ball also guarantees the immediate removal of specially defensive Hippowdon.
Set Details
The given EV spread is ideal for a special sweeper. A Timid nature is chosen, as Xurkitree's stellar Special Attack stat and access to Tail Glow means it is more beneficial to run a Timid nature over Modest to outspeed Mega Lopunny and neutral-natured Pheromosa and Choice Scarf Tapu Lele after Xurkitree has used Z-Hypnosis. Beast Boost increases Xurkitree's Special Attack upon KOing a foe, making boosted Xurkitree even harder to defensively keep in check.
Usage Tips
Even if Xurkitree successfully gains +1 Speed from Z-Hypnosis and sets up Tail Glow, its sweep is not necessarily guaranteed, as Choice Scarf users and priority move users can easily revenge kill it, and Xurkitree will have to rely on hitting Hypnosis to bypass Mimikyu and Focus Sash users. This means using Xurkitree is rather a risky move unless there is no other way its team can have the upper hand against the opponent. Xurkitree is best when deployed against defensive or balanced teams, which are sometimes not offensively oriented enough to reliably stop its rampage. Z-Hypnosis is best used against foes that Xurkitree naturally forces out or when Xurkitree needs a boost in Speed to avoid getting revenge killed by faster foes. Especially if Hypnosis was used on the forced switch, Xurkitree will be given a second chance to use Hypnosis in case the move misses or buy more turns to set Tail Glow. Against slower and defensive teams, Xurkitree can aggressively set Tail Glow on passive foes and start obliterating them with boosted attacks while possibly utilizing Hypnosis to shut down problematic foes. Lastly, much like all other setup sweepers, Xurkitree appreciates Stealth Rock, as it breaks Focus Sashes and makes Xurkitree less reliant on hitting Hypnosis to defeat their users reliably.
Team Options
Offensively inclined teams appreciate the presence of a Pokemon that can both pressure defensive teams and turn the tables of the match with Z-Hypnosis. Essentially most setup sweepers, such as Mega Salamence, Mega Blaziken, Mega Gyarados, and Mimikyu, appreciate the serious damage Xurkitree can cause on defensive cores or even buy a chance to safely set up if Xurkitree has put a foe to sleep. All aforementioned teammates have a good general performance against most other teams by virtue of better Speed, initial power, or unique ability in Mimikyu's case.
Since Xurkitree struggles to find a proper setup opportunity against many teams, it also appreciates offensive threats like Mega Salamence and Tapu Lele naturally drawing in walls like Celesteela or Porygon2, which Xurkitree can attempt setting up on. Bringing in Xurkitree with pivoting is also an option to grant it a favorable matchup, and Landorus-T and Pheromosa are capable of fulfilling this job. The former blanket checks Ground-types like Garchomp and opposing Landorus-T, while the latter can generate momentum with ease thanks to the number of switches it naturally causes to draw in foes like Celesteela, Tapu Fini, and Toxapex, all of which Xurkitree can threaten out and buy a turn to set up.
Lastly, just like every setup sweeper, Xurkitree appreciates Stealth Rock support so that it can rely less on Tail Glow in some matchups and bypass Focus Sash users. Dedicated leads that can set entry hazards and generate a setup opportunity with Yawn, such as Hippowdon and Swampert, are decent partners in this regard. Dual screens, Aurora Veil, and Memento users also greatly aid Xurkitree, as they give it more room to breathe and possibly let Xurkitree survive a hit which would KO it otherwise, reducing the risk involved from using Hypnosis. Landorus-T can make a lead and not only set Stealth Rock but also set Gravity for Xurkitree, letting it utilize Hypnosis much more reliably.