The Abyss is a "gargantuan vertical landscape divided into seven unique layers". In Minecraft, this ancient labyrinth is defined to be the region of the Overworld known as the Deep Underground, whose mouth begins at y = 0 and whose depth is unknown to this day. This mysterious formation mesmerized people. Valuable and dangerous primeval creatures and mysterious relics that are beyond comprehension beckoned adventurers looking to strike it rich. Over the span of many years, with a spirit of adventure for the unknown and countless legends luring them in, the world's only remaining unexplored chasm has swallowed up a great many people.

To those who offer up their bodies and challenge the chasm for which even darkness is no match, the Abyss is said to provide all. Life and death, Curses and Blessings — all of it. At the end of their journey, what fate will they choose to meet?

— Adage of the White Whistles

The Abyss is associated with feelings of loneliness, peril, and finality. To venture into the Abyss is to contend with sacrifice, making difficult isolating choices and dealing with the unlikelihood of messages making it to the surface. This is a place teeming with danger, beckoning delvers to be consumed by the warm darkness. This is a journey from which one is unlikely to return.

The Abyss is permeated by a mysterious Field, described as the "very blood of the Abyss", that seems responsible for or correlated with many of the eldritch phenomena surrounding the Abyss. Though this Field is everyflowing, everchanging, and everpresent, its concentration and effectiveness seems to be stronger with depth. The Field seems to be responsible for causing the Curse of the Abyss, a set of afflictions that seem to grow more severe with depth. The Curse of the Abyss does not seem to affect delvers who are descending into the Abyss, but those who are attempting to ascend out of it. In a sense, the Field can be visualized as a stack of thin sheets layered on top of each other. When descending, a delver passes safely through the sheets. When ascending, the sheets stretch around the delver. After a certain distance ascended, when a certain maximum number of sheets are stretched around the delver, further ascension pierces the old bottom-most sheet as the new top-most sheet is stretched around the delver, causing the delver to be hit by the afflictions. These afflictions, known as the Strains of Ascension, imply that the deeper one delves into the Abyss, the more difficult it will be to ever return. But in addition to these afflictions, delvers suffer passive afflictions from spending time within the Abyss, as their minds and bodies are literally warped by it, eventually being consumed.

The Strains of Ascension is the scientific name referring to the afflictions associated with the Curse of the Abyss. These Strains, shown below along with their Minecraft equivalents, differ in each layer and become more severe with depth:

• 1st Layer: Dizziness and nausea (exhaustion of hunger and thirst)
• 2nd Layer: Numbness and headaches (throbbing blur effect)
• 3rd Layer: Hallucinations and vertigo (sanity loss)
• 4th Layer: Bleeding and pains (regenerable damage over time)
• 5th Layer: Loss of all senses (complete blindness and deafness)
• 6th Layer: Loss of humanity (unregenerable damage over time)
• 7th Layer: Certain and immediate death (instant death)

At the bottom of the 5th Layer is what is known as the Absolute Boundary of the Abyss, beyond which lies the 6th Layer- the Capital of the Unreturned. Delvers descending beyond the Absolute Boundary are said to have made their "last dive" and considered lost forever, as ascending from within the 6th Layer results in the loss of one's humanity.