Here is my favorite set for BH:

Obstagoon @ Starf Berry
Ability: Harvest
Nature: Jolly
EVs: 244 HP / 252 Atk / 252 Def / 252 SpD / 252 Spe
- Substitute
- Protect
- Shift Gear
- Power Trip

Not to pat myself on the back or anything, but I think this is the best thing I've ever come up with. It's absolutely genius. Because Obstagoon is a Dark-Normal type, it can't get hit by Prankster moves, it can't get hit by Spectral Thief, and it gets STAB Power Trip. And while Obstagoon doesn't have legendary-level stats, it still has high enough stats to get the job done. This set works well with sun support, so you have a 100% chance to harvest a berry in berry range. Once you get the ball rolling on this, it's practically unstoppable.

- Substitute is essential to purposely chip yourself down to Starf Berry range. 244 HP EVs ensure that it takes exactly 3 Subs to activate the Starf Berry. It also blocks some status moves and Imposter.
- Protect is always a good move for scouting out your opponent. It also helps when you're in Starf Berry range to fish for a Harvest.
- Shift Gear is used when you're behind a Sub and your opponent hasn't broken it yet. It also ensures that you can outspeed the opponent to safely get a Sub up, as well as boosting your offensive pressure.
- Power Trip is a busted move, especially in this tier. With just one Shift Gear, it's already base 80 power, and each Starf Berry boost increases the power by 40.

COUNTERS:
-Zamazenta Crowned, especially if it's the Fur Coat variant, will wall this set hard. Not only does it resist Power Trip, but it has extremely high physical defense, especially with Fur Coat, and it can easily knock out Obstagoon with 4x supereffective Body Press.
-While Dark types block Prankster boosted priority moves, some moves, like Haze and Destiny Bond aren't blocked.
-Sound moves, like Boomburst, the ability Infiltrator can bypass Substitutes. (Infiltrator isn't used that often though.)
-Setting up with Obstagoon can be difficult, since it's not necessarily the fastest thing out there, and it can easily get overwhelmed by a fast offensive Pokémon, like Zacian Crowned and Galarian Zen Mode Darmanitan (which is a mouthful to say).
-Obstagoon can be picked off easily by a priority move at 25% health.
-Hazards and status can mess up Obstagoon's ability to set up properly.

In fact, I love this set so much that I have some variants of it: one uses Cheek Pouch and Recycle instead of Harvest and Protect, and another I'm working on will use Greedent's signature move Stuff Cheeks.