Trevenant

Trevenant, The Elder Tree Pokémon. This Pokémon is said to devour anyone daring to ravage the forest. To the creatures dwelling in the forest, it offers great kindness. Through its roots, it exerts control over other trees. A deadly curse falls upon anyone cutting down trees in forests where Trevenant dwell. It’s feared as a ghost of the forest. Lumberjacks bring along Fire types, which Trevenant hates, when they enter the forest. This Pokémon controls trees via roots stretching from its feet, and it will attack anyone that dares to ravage the forest.

Overview

The haunted tree, Trevenant is one of two Pokemon to introduce the new Ghost/Grass combination in XY alongside Gourgeist. However, while Gourgeist saw a lot of experimentation in XY during its infancy, Trevenant feel by the wayside due to its more aggressive nature which made it hard to compete with Celebi who shared many similar weaknesses, namely Pursuit Tyranitar and Aegislash, and was just better overall. Trevenant has some niches in the lower tiers as Ghost is a phenomenal offensive type and Grass isn't bad either, though neither complement each other's resistancew. However, Trevenant is a Pokemon that lacks a break out ability as its overshadowed defensively by Gourgeist XL due to better defensive stats and recovery, and now it has to compete with some offensive Grass powerhouses in lower tier formats such as Alolan Exeggutor and Kanto Exeggutor, as well as Roselia, Vileplume, and Silvally-Grass.
Positives
Wallbreaker - Trevenant's only niche in lower tier formats is as a wallbreaker due to its good attack and offensive typing, in conjunction with powerful moves such as Wood Hammer. This can make Trevenant more threatening than Pokemon such as Exeggutor and Alolan Exeggutor without support due to reliance of Sunny Day and Draco Meteor respectively. Horn Leech is also a boon in Trevenant's favor to heal off damage from Wood Hammer and switch-ins.

Negatives
Defensive Utility - While Grass is a nice defensive typing, Trevenant lacks the defense to truly make use of its typing on top of its susceptibility to being Pursuit trapped. This in combination with the other Grass options, such as Eviolite Tangela or Roselia, makes it hard to use Trevenant as a pivot when there are better options.

Abilities

Harvest - 50% chance of recycling a consumed berry each turn, 100% in sun - Neat in concept, worse than you'd hope. Renewable berries have a lot more use now with the rise of pinch berries but Trevenant lacks the offensive presence to take proper advantage of it, and it can't afford to fail that 50% chance with its shaky bulk and poor Speed.
Frisk - Reveals the opponents held item on switching in - This is alright, it can reveal a bait set every once and a while but its nothing exciting.
Natural Cure - Cures status when switching out - Not much to say here, curing status is very useful on any Pokemon and while this is best used by defensive Pokemon, being able to effectively sponge status moves is always helpful.

Movesets

Choice Band

-Wood Hammer
-Shadow Claw
-Horn Leech / Trick
-Earthquake / Rock Slide
Item Attached: Choice Band
Ability: Natural Cure
EVs and Nature:
252 Atk / 4 Def / 252 Speed
Jolly Nature

With a Choice Band to maximize its power, Trevenant can act as a solid wall breaker with Wood Hammer being the primary move. Shadow Claw is a strong secondary option as it lacks recoil and can hit more for neutral damage. Earthquake and Rock Slide are primary options for coverage allowing Trevenant to hit some key threats, such as Skuntank who resists both STABs, Pidgeot, Swellow, and Fire types. Horn Leech and Trick are other options available as Horn Leech will heal off Wood Hammer's recoil while Trick can cripple a wall.

Other Options

Substitute + Harvest - With Harvest and a pinch berry, Trevenant can become an annoying wall for some Pokemon to handle, setting up Substitute on a Choice locked move it resists and can threaten some powerful faster Pokemon more easily.

Possible Partners

Roselia - Due to it lacking the ability to pivot well and ability to spin block, Roselia can fill the role of bulky Grass while setting up hazards such as Spikes and Toxic Spikes to support the rest of the team. This can make Trevenant even more dangerous as the combination of hazards and Choice Band Wood Hammer can chunk a lot of threats.

Countering Trevenant

Skuntank - Without Earthquake, Skuntank is a hard counter to Trevenant resisting both STABs and Pursuit trapping it. Even with Earthquake Skuntank still has a strong chance of taking out Trevenant due to Choice Band locking it into a move.
Drampa - With Normal typing to make Shadow Claw a void move and resisting Wood Hammer, Drampa is a strong check to Trevenant as it forces secondary coverage, none of which are super effective. With Drampa's 135 Special Attack. this can become a losing situation fast for Trevenant as it can just OHKO something coming in or just remove Trevenant outright.

Locations in Games

Red/Blue/Yellow:
Not in game.

Gold/Silver/Crystal:
Not in game.

Ruby/Sapphire/Emerald:
Not in game.

FireRed/LeafGreen:
Not in game

Colosseum/XD:
Not in game.

Diamond/Pearl/Platinum:
Not in game.

HeartGold/SoulSilver:
Not in game.

Black/White:
Not in game.

Black 2/White 2:
Not in game.

X/Y:
Route 21.

Omega Ruby/Alpha Sapphire:
Evolve Phantump.

Sun/Moon:
Evolve Phantump

Ultra Sun/Ultra Moon:
Evolve Phantump

Let's Go, Pikachu!/Let's Go, Eevee!:
Not in game.

Animé Appearences

Trevenant has made a few appearances in the anime. Most notably, a Totem one helped out Ash and Kukui.

# -English Episode Name- -Jap. Episode Name- Pics
M17 Diancie and the Cocoon of Destruction The Cocoon of Destruction and Diancie Pics
841 Forging Forest Friendships! The Trevenant from the Wriggling Forest! Pics
1068 A Timeless Encounter! Ash: A Timeless Encounter! Pics
1069 Pikachu's Exciting Adventure! Pikachu's Exciting Expedition! Pics