How does the telepathy supernatural ability work?

Question

According to the MM books, telepathy is described as:

A creature with this ability (supernatural) can communicate telepathically with any other creature within a certain range (specified in the creature's entry, usually 100 feet) that has a language. It is possible to address multiple creatures at once telepathically, although maintaining a telepathic conversation with more than one creature at a time is just as difficult as simultaneously speaking and listening to multiple people at the same time. Source: MM, MM3

My questions:

• If a creature with telepathy knows that someone is within 100ft, can the creature communicate with that person, even if there is no line of effect or sight?

  My answer would be yes, because no book says that telepathy is blocked by walls, etc.

• Normally, a supernatural ability is a standard action to start. If the creature wanted to communicate for more than one round using telepathy, does the creature need to use up a standard action every round they are communicating or only in the first round?

  My answer is only in the first round, since the description says that maintaining telepathy is hard as speaking and listening normally.

• If a person the creature is communicating with moves out of the 100ft range, and then moves back into the range. Does the telepathic link need to be established again?

  My answer is yes, another standard action is needed to establish the telepathy between the two creatures.

I should add the telepathy is supernatural, and a character is looking at getting it from the Mindbender class (from Complete Arcane). And also get the Mindsight feat (Lords of Madness). I couldn't find anywhere to rule whether a supernatural ability should take a standard action every round it is on.

Answer 1

I treat telepathy just like speaking; it doesn't require an action to establish a link or whatnot. I could see requiring one if you want to start telepathically 'talking' to someone you can't see to represent the "mentally searching them out" part, and similarly if they go beyond 100' and then come back the telepath doesn't have any way except for normal sight or keeping trying to reach out telepathically to know that.

In general I agree with @PeterSeckler, interpret it whatever cool way you want and if PCs are finding some way to abuse it, toss in some limiters. I know a group would love a "can't be overheard and can work through walls" tactical coordination tool, but a little bit of "the rogue got dragged out of range/fell through a long pit trap" and "a psionic monster that can overhear telepathy just heard all your plans" from time to time compensates.

Answer 2

I really think that when no specific rule is mentioned (such as the 100' range) that you can just come up with whatever you think is cool. If (for example) the players accidentally free a telepathic demon and the demon follows them around and taunts them telepathically, I would just make up whatever details I wanted to about telepathy on the spot. For example, it doesn't specifically say in any monster manual that telepaths can influence a PCs dreams, but if I thought that sounded cool, I'd have that happen. Because..why not?

In a case where the telepaths are PCs instead of monsters there's probably more effort that should be paid to how the rules say the ability should work.. but even then, as long as it's a non-combat ability and it doesn't seem especially advantageous, I'd probably allow for plenty of creative interpretation.

Answer 3

Treat it like speech. If the creature knows there is someone there, but has no line of effect/line of sight to the target, it's more or less yelling in the dark. I can hear you calling out to me despite not seeing you, but unless you know where I am (I.e it's an ally and they said they were going up to their room at the Inn), it'd essentially just be a broadcast to anyone who could pick it up.

Answer 4

From Lords of Madness, p126:

Telepathy offers no special ability to sense other minds. The creature has to know that a being is there to communicate with it telepathically.

So if there is no line of effect nor line of sight, you must possess some other means (eg. detect thoughts spell or Mindsight feat) to discern the location of the creature, in order to communicate with it. The illithid elder brain's Telepathic Awareness (Su) works through solid stone, so I see no reason why Telepathy (Su) shouldn't work in the same way.

Similar to the clairaudience/clairvoyance spell, telepathic communication only functions on the plane of existence you currently occupy. Other spells that enable telepathic communication, such as dominate person, have this limitation.

An effect such as mind blank would block your ability to communicate with a creature in this manner.

Using a supernatural ability is a standard action unless noted otherwise.

The description doesn't explicitly state that it is not a standard action. Continuing a telepathic conversation over multiple rounds would require a standard action each round, just like concentrating to maintain a spell.