The Hollowing Wraiths Spell in Hollow Knight is a powerful up attack that is useful against flying enemies and bosses. Howling Wraiths can be upgraded to the Abyss Shriek spell which is the most powerful spell in the game and worth having for the tougher bosses.
This spell will allow you to attack enemies above you at the cost of 33 soul per attack.
How to find Howling Wraiths in Hollow Knight:

- Start from the Queen’s Station at the edge of the Fungal Wastes.
- Head up and to the left into Fog Canyon and continue to go to the top of the map and to the left.
- Eventually you will make your way over to an Overgrown Mound

- Fight the enemies in the mound to unlock a door at the top of the room and you will then find the Howling Wraiths.

- Once the enemies are defeated you can follow the path to the Howling Wraiths ability

You can upgrade the Howling Wraiths to the Abyss Shriek. The Abyss Shriek spell is the most powerful spell in the game and is very helpful when fighting bosses.