Moves
Wood Hammer is Trevenant's strongest STAB move, 2HKOing a majority of Pokemon that don't resist it and even some of the frailer ones that do, such as Magmortar, Swellow, and Pyroar, although it comes with hefty recoil damage. Shadow Claw is Trevenant's next best STAB option, with its better neutral coverage making it a decent move to throw out. It is also Trevenant's strongest attack against Psychic-types, particularly Xatu. Earthquake OHKOes Skuntank and Pyroar switch-ins, takes out Garbodor without making contact, and can hurt Steel-types such as Steelix and Aggron more efficiently. Rock Slide targets bulky Flying-types, such as Eviolite Scyther and Swords Dance Charizard, which can otherwise prove bothersome checks. Horn Leech is an alternative Grass-type STAB move for Trevenant to use that restores health instead of depleting it like Wood Hammer, making it decent for extending Trevenant's longevity.
Trick can be used to cripple the likes of Weezing, Vileplume, and Ferroseed while allowing Trevenant to switch up moves, although its attacks do lose substantial power upon doing so and Tricking Choice Band doesn't cripple many of Trevenant's checks. The aforementioned Poison-types might be holding Black Sludge as well, which puts pressure on Trevenant to Trick it away immediately, as it has horrible synergy with Wood Hammer. X-Scissor has mild use in skewering Malamar as well as OHKOing Shiftry switch-ins, though it doesn't hit much outside of that.
Set Details
Maximum Attack and Speed investment allows Trevenant to outspeed and threaten as much as possible, most notably Jolly Rhydon, Malamar, Adamant Golurk, and Adamant Aggron. An Adamant nature further increases Trevenant's damage output, while a Jolly nature allows Trevenant to outspeed Pokemon such as Modest Aurorus, Timid Omastar, Jolly Aggron, and opposing Adamant Trevenant if any of these are of concern. Choice Band bolsters Trevenant's power to the point where even resisted Wood Hammer does substantial damage to frailer Pokemon that resist Grass while suiting its hit-and-run attacking style. Natural Cure allows Trevenant to take on status users without fear, particularly letting it not being permanently crippled by Scald burns.
Usage Tips
Trevenant would preferably switch in on an attack it either resists or is immune to, such as Rhydon's Earthquake, Samurott's Waterfall or Aqua Jet, or Tauros's Rock Climb, or a status move from Pokemon that don't immediately threaten it, such as Toxic from Gastrodon or Thunder Wave from Musharna and non-Heat Wave Xatu. Alternatively, VoltTurn support from the likes of Swellow, Archeops, and Manectric can allow Trevenant to enter battle safely. Be wary of switching into Scald; even with Natural Cure ensuring Trevenant won't stay crippled, being burned on the switch means Trevenant would struggle to threaten the opponent's switch-ins. Once it enters battle, Trevenant should choose the move most capable of punching a hole through the opponent's team. Usually this move is Wood Hammer, as it has enough power to 2HKO, if not OHKO after Stealth Rock damage, the likes of Skuntank, Pyroar, Swellow, and Shiftry, which would be the opponent's most likely switch-ins given their resistance to both of Trevenant's STAB moves. However, Trevenant's low Speed and bad weaknesses mean it gets forced out really easily after using an attack or getting a KO, so it might be wise to go for the move with the most immediate results, which is when the other attacks and prediction come into play.
Team Options
VoltTurn teams allow Trevenant to enter battle without having to risk taking a direct hit and often absorb status moves or resisted attacks aimed at the VoltTurn users. VoltTurn Pokemon are also speedy, which helps cover for Trevenant's awful matchup against offensive teams. Flying-types such as Swellow, Archeops, and Scyther can use U-turn to pivot into Trevenant on various status moves and appreciate Trevenant threatening Ground- and Rock-types as well as softening up Steel-types for them. Primeape can U-turn away from Psychic-type switch-ins, such as Musharna and Xatu, for Trevenant to prey on, while Trevenant can cripple Poison-types with Earthquake or Trick. Lanturn and Manectric make for appealing Volt Switch teammates for Trevenant, as they can handle most Flying-type Pokemon, as well as Fire-type Pokemon in Lanturn's case, while Trevenant easily takes advantage of opposing Lanturn, Gastrodon, and Rhydon while also luring in and denting bulky Grass-types. Fire-types also can synergize well with Trevenant, as they offer speed, great offensive presence, and the ability to threaten most Pokemon that resist Grass, such as Vileplume, Weezing, and Scyther, which deter Trevenant from throwing out Wood Hammers. Trevenant meanwhile absorbs status for them and resists or otherwise covers for most of their weaknesses, including Pyroar's Fighting weakness and Combusken's Psychic weakness. Floatzel can be a good teammate for Trevenant, as it can revenge kill many of the Pokemon that would threaten Trevenant, while Trevenant can switch into Lanturn and Gastrodon and threaten them with powerful attacks, although switching into the former can be risky if they can Volt Switch into a Pursuit trapper.
