Gen 9 National Dex Monotype Defensive Nasty Plot (Psychic)
Celebi @ Colbur Berry
Ability: Natural Cure
Tera Type: Psychic
EVs: 248 HP / 92 Def / 60 SpA / 108 Spe
Bold Nature
IVs: 0 Atk
- Nasty Plot
- Giga Drain
- Earth Power
- Recover
Celebi has a niche as a defensive pivot for Psychic teams as a switch in to Water and Ground-moves while serving as a wincon against Water, Ground, Electric, and even Poison teams to an extent. Celebi having Natural Cure also allows Celebi to serve as a status absorber if needed. Nasty Plot boosting Celebi's Special Attack allow it to become a potent wincon against teams that don't have resists to Celebi's attacking moves. Giga Drain is used for the Grass STAB for this set due to its ability to restore some HP, which is useful to make sure Celebi doesn't have to use Recover as much. Earth Power targets Poison- and Steel-types such as Toxapex, Archaludon, Gholdengo, Heatran, Hisuian Goodra, Empoleon, Magnezone, Galarian Slowking, Alolan Muk, Iron Treads, and Excadrill super effectively. Recover is used to give Celebi reliable HP recovery so it can stick around longer to check Water, Ground, and Electric teams.
248 HP EVs are used for bulk. 60 Special Attack EVs are used to allow a +2 Earth Power to 2HKO Toxapex. The given Speed EVs allow Celebi to outspeed Jolly Mega Swampert outside of rain as well as Gholdengo that uses 224 Speed EVs and isn't Timid Nature. The rest of the EVs are used in Defense with a Bold Nature to give Celebi some physical bulk. You can use a more bulkier EV spread such as 248 HP / 176 Def / 60 SpA / 24 Spe with a Bold Nature, being useful to outspeed Max speed Modest Magnezone.
The kicker of this set is Colbur Berry. Colbur Berry Celebi was a thing back in Gen 6 Monotype and is useful in Gen 9 National Dex Monotype. With Colbur Berry reducing the damage taken from Dark moves, this defensive Nasty Plot Celebi set serves as an effective lure against Water/Dark Pokemon such as Greninja, Hisuian Samurott, Mega Gyarados, and Mega Sharpedo, which is really useful to live a hit from them and remove them in the Water matchup. Colbur Berry is also nice to serve as a Knock Off Switch in if it needed.