The Abyss

The Abyss is the lowest area in Hallownest, located below Ancient Basin. It is the place of origin of the Void, a substance found at the bottom of the Abyss.

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 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.

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.

The Abyss can be accessed by going to the bottom of Ancient Basin and by having the King's Brand to unlock the entrance.

The Void Tendrils and Siblings found here become passive once Void Heart has been acquired.

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.

Birthplace
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.

Trivia

 * 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 expansions would have "taken players down into the lake of void, to explore the twisted space within."
 * 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.

Древний котлован O Abismo