The area itself contains a giant chasm which is littered with the shells of Vessels who were born in the Abyss and then discarded. An additional area in the chasm can be opened when the Kingsoul is equipped, which leads to an egg that can be Dream Nailed to obtain Void Heart.
To the very west is an altar surrounded by numerous screaming faces where Abyss Shriek can be acquired. The sea of Void is located on the east side with a lighthouse standing on its shore. This lighthouse can be activated to calm down the Void Tendrils in the sea which normally lash out towards intruders. The Shade Cloak can be acquired to the east of the sea, in a room with a corpse holding a bowl of Void.
The Void Tendrils and Siblings found throughout the Abyss become passive once Void Heart has been acquired.
Before the kingdom of Hallownest was founded, an ancient civilisation originated from or near the Abyss who worshipped the Void. When the Pale King arrived in Hallownest, he eventually discovered the Abyss and the presence of the Void. He used the Void to turn his children into Vessels, beings with a shell filled with Void who were born in the Abyss. The Pale King sealed the Abyss after selecting the Hollow Knight as his chosen Vessel. The shades of dead Vessels, the Siblings, still wander the bottom of the Abyss.
How to access
The Abyss can be accessed by going to the bottom of Ancient Basin and by having the King's Brand to unlock the entrance.
Lifeblood Core Room
The Abyss contains a door which requires 15 Lifeblood Masks to open, which is most easily opened with Joni's Blessing in conjunction with other lifeblood sources. When the Knight approaches said door with 15 Lifeblood masks, the 15 orbs next to the door will begin to glow, one by one, until the last one is shining a bright blue hue and the blue vines disappear, leaving behind a glimmer with the same bright colour as the orbs. Inside this room, the Knight will go through a series of platforming challenges before getting to a room with a platform, and, on it, the Lifeblood Core charm. In the background of this room is seen the massive multi-eyed head of the Abyss Creature. After obtaining Lifeblood Core from this room, the Knight will wake up next to the vine door, which now has a grey tone, and the room can no longer be entered, and the Arcane Egg contained inside will not be obtainable if missed.
The birthplace of the Knight. Accessible only with the Kingsoul Charm equipped. Its entrance is located at the bottom of the Abyss on the west side. At the end of the area is an egg which, upon being hit with the Awoken Dream Nail, reveals a scene from the past involving Vessels and the Pale King.
This room is located in the southwest part of the Abyss. Upon entering the Knight can jump on top of the pedestal at the centre of the room. Using the Spell Howling Wraiths while on the pedestal grants the upgrade to Howling Wraiths, Abyss Shriek.
If the faces in the background are Dream Nailed it will read: "...Our voices… will cry out… again...". No other dialogue can be found in or about the room. Other than giving the Knight the Howling Wraiths upgrade the room serves no other purpose.
In order to access this room the Knight first needs to get past the Void Lake by turning on the Lighthouse.
After swimming through the Void Lake and obtaining the Shade Cloak, a room on the northwest near where the Shade Cloak is acquired can be accessed. It has a small shaft of light and a Shade Gate which will lead to a hallway connected to the ceiling and in turn a small study of sorts overlooking the Void Lake.
In the study, there is a fossilized entity of sorts that if interacted with will give the Void Tendrils Hunter's Journal entry. The text associated with this interaction is "An imprint of Abyss given form."
- According to the Kickstarter stretch goals, the Abyss was "a massive new expansion for only the hardiest of adventures" and was going to have "4 new bosses", however, this $85,000 stretch goal was not reached. According to Team Cherry, the expansion would have "taken players down into the lake of void, to explore the twisted space within."
- When later asked on Creative Hustler's Show in October 2017, it was stated that Team Cherry would not be working on the content planned for the Abyss expansion, citing that the world for the game was built without considering this expansion, and that Team Cherry would like to move on from Hollow Knight and work on a new game in the near future.
- The lighthouse in the Abyss was originally going to feature a boss encounter. A sketch of this boss was shown by Team Cherry on Twitter, but the boss itself was never added.
- This area does not have a map, instead being shared with that of Ancient Basin. It also does not appear on the zoomed-out version of the map, but does when zoomed-in.
- The Abyss ambience is the Main Menu theme distorted and slowed down.