Telepathy

Matters of mind to mind

"Now, reach out to the world around you. You'll feel a concentration of energy, like a halo, around the head of every person. Choose one, focus on it--- and break in."

— Alexia Shantorn, psionics mentor

The second class of psionics, telepathy is the practice of using your psionic power to touch, or breach, other peoples' minds. A talented telepath can read thoughts, send messages directly into someone's mind, make people see, hear, or think different things, and even control others.

Basics

There are two types of telepathic connection: transmission and breaching. Transmission it simply involves reaching out to a nearby person's mind and sending a one-way signal. Transmission differs from breaching in that the person on the other end has not put up any mental defenses and accepts the incoming message without resistance. Breaching is required when using more intrusive powers -- it requires the psionic to overcome their opponent's mental barriers to transmit the power, which costs more energy. Breaching is also needed with simple messages if the connection decides that they don't want to accept any incoming transmissions, and consciously or unconsciously put up mental barriers.

Sensation

After a psionic reaches out to someone's mind, when they connect, the sensation has been described as feeling like a brief cold breeze brushes your brain. However, if the connection is resistant and breaching is needed, the sensation changes to feeling "hot and pressurized." The stronger a psionic pushes on the barrier, the hotter and denser the sensation gets, until the barrier finally breaks and a gust of cold is let out all at once.
On the other end, when someone is on the receiving end of a telepath's transmission, the sensation has been described as a static feeling and a sense of otherness prior to and during the message. Meanwhile, trying to resist a breach can produce a hot and prickling sensation that worsens with the intensity of the breach and intrusiveness of the power. Intense resistance becomes painful and distracting, and whether or not a person's mind will be breached sometimes comes down to whether the breacher or the breachee has a higher pain tolerance.
Once an unwilling person's mind has been breached, there is a small window where the psionic can send any messages or commands they wish. They can extend this window by concentrating on keeping their opponent's barriers down, but if they lose focus or get distracted, the opponent gets a chance to reestablish their mental barriers. How long it takes for this to happen varies from person to person.

Notable Powers

The higher the level of a power, the more difficult it is, and the more energy it requires to use.

Level 1 - Novice

Simple Messaging: One of the first powers psionic-in-training learns, simple messaging involves reaching out to another's mind and transmitting information, usually in the form of a pseudo-audio message. Transmitting messages in the form of simple emotions also falls under this category.

Skim Thoughts: Though this power technically counts as breaching, it is relatively unintrusive -- by breaking down someone's mental barriers slightly, one can glean their surface-level thoughts and feelings as fragments.

Level 2 - Training

Read Thoughts: By poking a hole in someone's mental barriers, a psionic can tune in to their stream-of-consciousness thoughts and prevalent emotions. A keen person can realize when their thoughts are being read, especially if the psionic is not trying to be subtle, but for many, this power is hard to notice.

Sensory Messaging: A milder precursor to the Hallucination power, this power sends messages not as thoughts but as sounds, sights, or sensations. It requires a light use of brain-body reversal, and therefore can often be unintentionally resisted against by people who subconsciously avoid the mild pain associated with it, so it's best used on those who have been told ahead of time that it'll be used to contact them. A psionic talented in the skill can send messages that present themselves as text flashing across one's vision, audio that seemingly comes from an outside source, or letters tracing themselves into the palm of one's hand. This power is not as efficient as simple messaging, but its main benefits are that it can communicate images and specific audio recordings that could not be sent with simple messaging.

Thought Link: This power establishes a mental link of simple messaging between two individuals -- and can include non-psionics. It requires a higher energy cost to establish the link, but a much lower burn to send messages once it's been established. Thought links simplify a method of communication between a psionic and a non-psionic where the psionic sends a message, then reads the recipient's thoughts for their response. However, reading thoughts is messy, the psionic might not have enough energy to continue this method for long periods of time, and the non-psionic might not want all of their thoughts read. Thought links function essentially as mental walkie-talkies -- each person can choose what messages they want to send and when.

Slow: This power functions by channeling psionic energy to stem the flow of information from the brain to the muscles. The target's movement becomes slower and less forceful, as if they are underwater. The slower the psionic tries to make their target, the more energy the power uses.

Level 3 - Advanced

Psionic Sight: A difficult power to keep active for a long time, psionic sight requires the user to apply partial brain-body reversal to themself in order to make their eyes see all the psionic energy in a certain radius that their brain can feel. Psionic sight reveals concentrations of psionic energy (a.k.a. people) in an area, even through walls and barriers, as well as flows of energy that are controlled by other psionics. For example, someone using this power would be able to see another telepath reaching out to control someone else's mind, or see which electrical systems an electrophage is drawing energy from. When not using any powers, a psionic viewed through psionic sight looks like any other non-psionic, but their energy greatly expands when they are using their abilities.

Freeze: A more powerful version of slow, this ability completely stops commands from traveling from the brain to the muscles, freezing the target in one position. The effect is stronger farther away from the brain; so a frozen person might be able to blink and look around fine, talk with some effort, be able to breathe but feel like their chest is very compressed, barely be able to move their shoulders and arms, and feel like their legs and lower body are completely immovable.

Hallucination: A more malicious use of sensory messaging with the intent of tricking or causing fear, this power uses partial to complete brain-body reversal to make the target see, hear, or feel things that aren't there. This is usually painful for the target, so is most often used for causing fear or distraction in a fight, but expert psionics can expend extra energy to dull the nerves enough to make the pain unnoticable, which is extremely useful in tricking or decieving a target without tipping them off.

Level 4 - Expert

Control: By hijacking the pathways the brain uses to send commands to the muscles, a psionic can send their own commands to another person's muscles, effectively taking control of their body and movements. Unless the psionic uses this power at the same time as Hallucination or Induce Unconsciousness, however, the target is still aware of their actions and surroundings as they still have access to their sensory organs, including nerves. Most scholars classify this power as a further step up from Freeze, but some think that it is its own unique power.

Induce Unconsciousness: A psionic can cause their target to faint by triggering a specific and difficult-to-reach part of the brain to shut down mental processes and go unconscious. For psionic and trained non-psionic targets, this power can be difficult to resist as it happens quickly and doesn't register to the brain as a form of breaching, so the brain doesn't automatically resist it. Therefore, people who have their guard up can sometimes counter it, but a relaxed or unaware target has a small chance of fending off this power. The difficulty of resisting this power also scales with the strength of the psionic (which hopefully goes without saying), as it takes longer to induce unconsciousness for a less practiced or talented psionic than it does for an expert one.

Total Hallucination: By overwhelming all or most of a person's senses, a psionic can induce what's called a total hallucination. In this state, a target has no contact whatsoever to the real world through any of their senses, and only sees, hears, and feels what the psionic wants them to. This state is usually painful for the target, as it requires a total brain-body reversal, so its use in deception on unwitting targets is limited. However, expert psionics can manipute the target's nerves to dull this pain and make it unnoticable. These talented psionics are somewhat rare and highly sought after.

Deep Delve: The most thorough and difficult form of reading thoughts, deep delving is an ability that lets its users search not only a target's surface and subconscious thoughts, but explore their mind, discover their motivations and feelings, and even witness memories. It usually takes a long time and is very intrusive, so this power is unsuited to thought reading on-the-go and is most often utilized when interrogating targets.

Resistance Training

Technically, everyone has psionic energy. However, only psionics are able to feel this energy and extend it into the world around them. Non-psionics may not be able to do this, but they can still command the energy within the borders of their own mind. As a result, even non-psionics can become proficient in resisting mental breaches -- their brain, their territory.
Some megacity districts hold "Resistance Workshops" where ordinary folk who want to protect their thoughts from telepaths can learn to hone their resistance. It's tricky as non-psionics can't feel or measure their own psionic energy, but a useful skill nonetheless. It is common for upper-class citizens to take these workshops or hire personal resistance trainers, as they can protect their personal or business secrets from rivals -- not to mention, they can afford it much easier.

Brain-body Reversal

When a psionic tries to induce hallucinations, slow or freeze someone, use psionic sight, or transmit sensory (auditory or visual) messages, they have to perform what is known as a partial brain-body reversal.
Normally, information flows from someone's nerves and sensory organs to their brain. However, when a psionic tries to use any of the aforementioned powers, they have to reverse the flow of information -- make it flow from the mind to the senses.
In the case of psionic sight, the telepath does it on themself; they take the feelings of the psionic energy around them, and force their eyes to visualize it. Slowing or freezing someone is slightly easier -- commands flow from the brain to the muscles naturally, and the psionic doesn't have to reverse that flow; they just have to stem it.
Conversely, total hallucination of all senses is very difficult as it requires a total brain-body reversal. The majority of the energy put into a total hallucination goes to reversing the flow of every nerve in the body so that the victim feels what the psionic wants them to feel.
The sensation of brain-body reversal has been described as "mildly painful, uncomfortable, and headache-inducing." However, talented psionics can finesse their reversals so that their targets don't feel anything, and therefore realize that they are being influenced.

"Whenever I'm stationed in a fringe city, people constantly ask me to look at 'em with psionic sight and see if they've 'got the gift.' I always gotta tell 'em: first of all, it don't work like that. Unless you're readin' my mind right now, you'll look just like a regular person to me. Second of all, usin' psionic sight too long gives me a migraine for the rest of the day. I'm not sufferin' that to satisfy the whims of some fringe folks."

— A psionic IRUS soldier

"It started with a pressing feeling in my head, when the interrogator sat in the chair across from me. Then it got worse, and my temples started hurting like hell. I thrashed around, but my hands were chained to the table. Then he broke through, and I think my vision clouded a bit. It didn't hurt anymore, but I could feel him rooting around in my head. It was awful. I don't know how long it lasted. Maybe five minutes, maybe an hour. I'm sorry, boss. I couldn't keep him out when he asked about where I stashed the firearms."

— A woman recounting her deep delve by a psionic IRUS officer