Elementals created from the spell of summon elemental should have intrinsic telepathy so if you also have telepathy, you can always find them.

Artifact helm of telepathy, neutral aligned, that either enhances or blocks telepathy level-wide based on whether you have it from some source other than the helm (or alternatively, it’s not a helm of telepathy, and just bases things on whether you are telepathic), and grants a Charisma-based bonus to your armor class.

If you do have telepathy, all other monsters get telepathy too and you can sense them, and they will be affected by telepathy-targeting effects, including yours if you have any psionic abilities.

If you don’t have telepathy, all other monsters will be treated as if they are not telepathic, even if they are; they will also be blocked from using any mind blasts or other psychic powers.

If you have telepathy, you should hear the quest leader’s telepathic summons message more clearly than its current garbled state (perhaps “m..ic transporter”), and if you have extrinsic telepathy, you should hear it with perfect clarity.

Telepathy currently sees things with minds. Change it (or perhaps change only the amulet of ESP, leaving other telepathy the same) so that it sees things with souls instead of minds. Mostly this corresponds with the same monsters (with a few exceptions such as mummies which are animated by the soul of the dead person), but if a monster with a soul is polymorphed into a form that normally doesn’t, it retains its original soul, and shows up as its original form to ESP.

Additionally, ESP shows the spirit of a humanoid with a soul just after you kill it if you’re blind, making some angry or resigned gestures before fading away.

Intrinsic telepathy only works in a radius equal to your Int (extrinsic sources aren’t changed). Cooperative telepathy, if implemented, works in the same radius if intrinsic, full-level if extrinsic.

If you can see a monster only with telepathy, you cannot see its peaceful/hostile status, so all monsters appear hostile by default (except tame monsters, which you can still see as tame). Likewise, you can’t see the monster names of non-tame monsters you can see only with telepathy.

Ranged divination effects (monster detection, object detection, clairvoyance, maybe telepathy) are suppressed if the level is not mappable.

Some monsters can block being detected by your telepathy, either innately (disenchanters, perhaps) or as a monster intrinsic conferred by armor (such as a tinfoil hat) or spellcasting by an ally. Also, possibly allow for area-of-effect “telepathy dead zones”.

In certain cases, you can see what telepathic monsters can see in a radius of 2 or 3 centered on the monster, assuming it fails a saving throw versus you reading its mind.

You can pray at a gravestone, or possibly ring a bell at one, to cause any of a number of good and bad effects:

• Summon a ghost, which might be hostile or peaceful.
• Summon a hostile undead, flavored as it forcing its way up out of the grave. Usually a zombie.
• Polymorph you into a zombie or mummy of your own race.
• Put you to sleep, ignoring resistance.
• Create a swarm of hostile manes or lemures.
• The headstone falls on your foot, dealing some damage, less if wearing boots (“killed by a falling tombstone” if fatal).
• If the grave is a bones pile grave, the ghost of the player always appears. It will be peaceful if their alignment matched your own and hostile otherwise.
• Various cosmetic messages that do nothing. “The air suddenly turns cold.” “The engraving on the headstone shimmers for a moment.” “A shiver runs down your spine.”
• The dirt cracks open and spits out any items buried under it.
• A voice from nowhere whispers a random rumor, true or false.
• The epitaph on the grave changes. This does not flag the grave.
• Get an alignment bonus for honoring the dead (this is only if triggered by praying). “You feel that the one buried here is content.” Bonus might be larger if you’re lawful or a Priest, probably 1 otherwise. This should possibly happen before and independently of any other effects.
• Limited identify of 1 item.
• Type-identify of multiple un-type-identified items in the inventory, but the player doesn’t get to pick which. Might pick 0 items (flavored as the spirit not knowing anything new about what the hero is carrying).
• Enlightenment.
• Temporary telepathy / sleep resistance / infravision / other intrinsic.
• The gravestone rumbles and moves aside, revealing a branch staircase to a just-created-now one-level branch, a small one-off “crypt” floating branch that contains some undead, some boxes containing corpses, and some treasure. This only happens on gravestones in the Dungeons of Doom.
• You “feel that the dead are restless”, aggravating monsters level-wide. All gravestones on the level become flagged against further attempts. This effect could be added to and independent of other ones, and if so, it’s a chance dependent on the number of already flagged gravestones on the level, which provides a nice way to balance it on levels that have massive amounts of gravestones.

After you get one effect, the gravestone is flagged so that it doesn’t happen again (or, more evilly, that any further attempts will only result in bad effects). Possibly shouldn’t work at all on graveyard levels, because they have too many graves to balance these effects.

Rings carried by Nazgul are all artifact rings of invisibility. They autocurse and also confer telepathy, see invisible and aggravate monster.

If you are a Caveman, you get telepathy or clairvoyance while you are hallucinating.

Artifact chaotic amulet Amulet of Splendor: provides every single amulet effect, as well as unchanging-ignoring controlled polyself when invoked. Wearing it conveys life saving (this WILL disintegrate the amulet if triggered), magical breathing, unchanging, poison resistance, ESP, reflection, strangulation (doesn’t kill you due to magical breathing but maybe it makes it so you can’t eat food or something while wearing it, or it autocurses), restful sleep, and gender change for as long as you wear the amulet. Base type is a cheap plastic imitation of the Amulet of Yendor.