You can only get one copy of BlackGlasses in Pokémon Black & White, and you’ll find them on the ground in the Desert Resort.
The Desert Resort area is located in the northwest corner of Route 4.
As for the item itself:
When held by a Pokémon, the BlackGlasses boosts the power of Dark-type moves by 20%. It’s an ideal item to pair with hard-hitting Dark-type Pokémon.
BlackGlasses Location (Step-by-Step)
Step 1: Starting at the Nimbasa City Pokémon Center, head east towards the city’s exit.
Step 2: Keep walking east through the city, passing the Battle Subway.
Step 3: Turn and head south through the green tunnel to exit Nimbasa City.
Step 4: The tunnel’s exit leads to Route 4. From here, just keep south on Route 4.
Step 5: Continue south, passing the hiking trainer.
Step 6: Above Route 4 is a bridge overpass, but just continue south through the other side of the overpass. Then turn to head west onto the available road.
Step 7: Continue west here, then head north at the corner of the road.
Step 8: Keep north on this road, passing under the overpass again.
Step 9: The path leading north will take you through to an area with heavy sand.
So just keep going until the road ends, then turn left at the corner to keep following the path.
Step 10: Continue west through the sand past the Doubles trainers.
Step 11: Keep west until reaching the tunnel leading to the Desert Resort (you’ll see it along the northern wall). Head straight through the tunnel.
Step 12: Now at the Desert Resort, head north past the two trainers.
Step 13: Continue north over the sand dunes and past the hiking trainer.
Step 14: You should see the BlackGlasses as a Poké Ball item sitting in a sand pit directly ahead.
What Do the BlackGlasses Do?
The BlackGlasses are a held item that increases the damage of Dark-type moves by 20%.
It’s best to give this item to a Dark-type Pokémon so that Dark-type damaging attacks receive the STAB (Same-type attack bonus) boost in addition to the BlackGlasses bonus.
When held by a Pokémon with a strong Attack/Special Attack stat, BlackGlasses can boost a move to one-hit K.O. potential.
Absol and Bisharp are both great Physical attackers that could pair nicely with the BlackGlasses. Both of those Pokémon can also learn Sucker Punch, which ends up at a base Power of 144 with both the BlackGlasses and the STAB bonus in effect.
- Where To Get the BlackGlasses in Pokémon Black & White