Telepathy

Telepathy, sometimes referred to as ESP, is a passive property in NetHack that allows you to detect non-mindless monsters, regardless of whether or not you can physically see them.

Description

The range of unblind extrinsic telepathy is indicated by flags. In comparison, the range of warning is slightly greater, and is indicated by question marks.

Telepathy can be acquired as both an intrinsic and extrinsic property through various means, and function somewhat differently depending on their source. It is possible to have both forms of telepathy independent of each other, with the extrinsic property taking priority over the intrinsic.

• Intrinsic telepathy allows you to detect all non-mindless monsters on the current level, but only while you are blind.
• Extrinsic telepathy allows you to detect all non-mindless monsters within a radius of 8 squares, and additionally displays all non-mindless monsters on the current level while you are blind.

Only three monsters have intrinsic telepathy:

• e floating eye
• h mind flayer
• h master mind flayer

If a mind flayer or master mind flayer is near you while you possess either form of telepathy, they can detect you and will attack you with a long-distance psionic blast for d15 damage; polymorphing into a mind flayer allows you to use this ability with the #monster extended command.

Intrinsic sources

Intrinsic telepathy can be acquired through the following methods:

• Eating the corpse of a floating eye (100% chance) or a (master) mind flayer (50%)
• Eating an amulet of ESP
• Polymorphing into a monster with telepathy (i.e., a floating eye or either mind flayer)
• Praying to your god under certain circumstances

Intrinsic telepathy can be lost if you are either hit by the gremlin's intrinsic-stealing attack at night, or else commit murder as a lawful or neutral character.

Extrinsic sources

Extrinsic telepathy can be acquired through the following methods:

• Wearing an amulet of ESP, including the Eye of the Aethiopica, or a helm of telepathy
• Carrying any of the following artifacts:
  • The Longbow of Diana
  • The Orb of Detection
  • The Magic Mirror of Merlin
  • The Platinum Yendorian Express Card

Strategy

Both forms of telepathy are considered among the more useful methods of detecting monsters, as they allow for much safer movement (especially involving pets) if blinded unexpectedly, e.g. an exploding yellow light. However, the late game contains dangerous mindless monsters such as the stronger golems and green slimes; telepathy is best supplemented with other forms of monster detection, such as warning.

Telepathy also grants players the ability to prepare for or path around especially dangerous monsters depending on their strategy. The intrinsic is usually considered sufficient for such purposes - it is sought out enough that some Monk players will break vegetarian conduct and eat a floating eye corpse in order to obtain it. Telepathy can also be obtained from prayer, though this requires management of high Luck and a co-aligned altar, and is generally the ideal source of the intrinsic for foodless or vegan players; extrinsic telepathy is preferred for conducts that rely heavily on awareness of your surroundings, such as pacifist.

Telepathy and monsters

Players very often keep a blindfold or towel on hand for telepathic characters so they can blind and unblind at will to scan their current level; this is frequently done to seek out specific monsters, e.g. looking for lost pets, discerning the exact location of Medusa on some variations of her level, or even finding the Riders on the Astral Plane. As both forms of telepathy display monsters while blind, some players may mistake this as being exclusive to the intrinsic property.

The mental blasts of mind flayers only occur if you currently have telepathy, and can be counteracted by temporarily removing or stashing whatever extrinsic telepathy source you have. This is not always applicable, and is often unnecessary in practice anyway - the damage is usually negligible outside of scenarios involving early minesflayers, or else escaping from other monsters while at low HP. See the article on mind flayers for other strategies dedicated to handling them in combat.

When employing boulder forts against specific threats, telepathy is useful to scan the area and keep track of their location. Seeing a monster via extrinsic telepathy also makes it a valid target for the cone of cold and fireball spells when cast at Skilled or higher level in attack spells.

Artifacts=

Artifact wishes that come after most (or all) other essential properties are covered will usually prioritize sources of telepathy. With the exception of the Eye of the Aethiopica, all artifacts that give telepathy grant the property while carried, preserving slots for other properties. Monks in particular aiming to preserve vegetarian or vegan conduct may opt for these artifact wishes.

• The Magic Mirror of Merlin is lawful and also gives magic resistance, and is an ideal wish target for lawful Monks.
• The Platinum Yendorian Express Card is neutral also provides magic resistance and half spell damage, and can be invoked for charging, making it one of the most desirable artifact wishes.
• The Eye of the Aethiopica is neutral and a highly-desired artifact for most spellcasting-focused characters - carrying it alone grants half spell damage and faster energy regeneration, while wearing it also provides telepathy and magic resistance at the "cost" of the amulet slot.

Zen conduct

Telepathy is an absolutely vital intrinsic for zen conduct play: starting the game being unable to see monsters while blind will leave you at the mercy of molds and anything with a passive attack, or more likely the wrath of a peaceful monster that you angered by bumping into them. In particular, telepathy enables zen characters to safely navigate shops without angering the shopkeeper, which is almost always game-ending if it occurs.

Origin

Telepathy is the ability to transmit information from one person's mind to another's without using any known human sensory channels or physical interaction. The term was first coined in 1882 by Frederic W. H. Myers, a founder of the Society for Psychical Research (SPR), and is among the more popular concepts of thought-reading; the concept emerged in the context of significant advances in physical sciences of the era, where scientific concepts were applied to mental phenomena in the hopes of understanding other events considered paranormal (i.e. beyond the understanding of science at that time). As the scientific disciplines progressed in development, telepath experiments have been criticized for a lack of proper controls and repeatability, and the topic is generally considered pseudoscience due to lack of good evidence.

ESP is an abbreviation for ExtraSensory Perception, which refers to any perception not gained through the body's physical senses. The term was coined by parapsychologist Joseph Banks Rhine in his 1934 book (also titled Extrasensory Perception), and encompasses a number of purported psychic abilities, including telepathy and clairvoyance, among others.

Messages

You feel a strange mental acuity.

You gained intrinsic telepathy from eating a corpse.

You feel in touch with the cosmos.

As above while hallucinating.

A wave of psychic energy pours over you! It locks onto your telepathy!

A (master) mind flayer is on the same level as you and attacking you via telepathy.

Variants

SLASH'EM

In SLASH'EM, the potion of ESP can be quaffed to grant intrinsic telepathy temporarily if uncursed; a blessed potion grants the intrinsic permanently, while a cursed potion removes the intrinsic if you have it. This provides a viable source of the intrinsic for vegan players, especially Monks.

The Crown of Saint Edward is an artifact helm of telepathy that serves as the Yeoman quest artifact, and additionally provides magic resistance and half spell damage, making it another enticing artifact wish for lawful players.

xNetHack

In xNetHack, gnomish wizards, kobold shamans, and orc shamans are telepathic, and may infrequently grant intrinsic telepathy when eaten.