Fore note: those are information I could gather from the canon The Sentinel universe as well as some bits from AUs of the TV Show. It’s simply a little guide on what that trope is and what its basis are, so do what you will with this. All of this can obviously be altered/used/ignored to fit your universe, every aspect of this is up to you.

Sentinel/Guide

General

I) Most seen AU set-ups:

• Sentinels/Guides are known (and given freedom/respect)
  
• S/G are known and one is subjugated or enslaved to the other
          
• S/G are not widely known
  

II) In some AUs, S/G have that notion of ‘pack dynamic/structure’ similar to a/b/o where the ranking can be done through some sort of strength-level comparison between S/G

III) In some universes, S/G can be a societal institution managed by military or non-military bureaucracies, or organized in packs

IV) A ‘spirit world’ can exist that usually both the S/G can access, it can also be where they can communicate with their spirit animal if they have one

About Sentinels

I) A Sentinel is, in their most basic form, a person with one or several heightened senses (= sight, hearing, touch, smell, taste), and/or heightened abilities (if they have magical/supernatural powers for example)

II) As mentioned before, a Sentinel can possess additional abilities on top of their enhanced senses. Examples from the TV Show:

• ability to speak with ghosts
          
• have visions
          
• have a spirit animal
  

II.5) Q: What is a spirit animal? A: a spirit animal is characterized as a teacher/messenger/protector that comes in the form of an animal and has a personal relationship to someone.

In the TV Show, a Sentinel’s spirit animal rarely made a physical appearance, but instead would serve as a guide in dreams and vision to ‘communicate’ with the Sentinel. The spirit animal wouldn’t speak out loud but instead run or hiss/growl to provide guidance.

Some spirit animals can have mystical powers. Example: in the TV Show, the Sentinel’s spirit animal resurrected the Guide.

III) A Sentinel, if they get overwhelmed by those hyperactive senses and the sensory input grows to be too much can:

- go into what is called a ‘zone-out’

- become hyper aware/over-focused on one of those senses

IV) A Sentinel can show their abilities at youth and/or later through a period of isolation and intense focus on the surroundings

V) Examples of what a Sentinel can do or their abilities’ liability:

• read a fine print on a newspaper from dozens of feet away
          
• know how many people are in a room through the body warmth the Sentinel can sense in         the other room
          
• focus on someone’s heartbeat to know if they’re lying or not
          
• hear a pin drop in an apartment across the hall
          
• …etc
          
          
          
• smells becoming repugnant/unbearable
          
• regular fabric being too itchy and irritating the skin
          
• bright lights/colors causing headaches
          
• if one or more senses get aggravated too much, from high input, they can cause         ‘spikes’, a sudden pain coming from the area of the sense
          
• …etc
  

VI) Sentinels can — or not — be possessive, obsessive, primal and/or territorial over a Guide, and the same things can be attributed to Guides

About Guides

I) A Guide helps a Sentinel understand/control/deal better with their super senses/abilities. They ground a Sentinel and are a calming influence on them.

II) A Guide is often the only one able to help a Sentinel through a zone-out or ease a ‘spike’ when one happens

III) Examples of how a Guide can help:

• be physically close to the Sentinel
          
• teach and use a system of ‘dials’ from 0 to 10 where the Sentinel dials up or down their         senses: 0 = the senses completely shuts off, 4-5 = regular human level or most comfortable one for the Sentinel, 10 = level that leads to zone-outs or spikes
  

IV) A Guide can also have extreme empathy and/or psychic abilities like:

• foresight
          
• telepathy
          
• ...etc
  

About ‘zone-outs’

I) Those zone-outs are often shown by the Sentinel becoming so focused on one sense alone, that they subconsciously close off all input from their other senses. The Sentinel then feels ‘lost’ in that one sense and falls into a catatonic state.

II) It can start by feeling stressed, disoriented and/or drugged, for example

III) The Sentinel is not necessarily dependent on a Guide to come out of a zone-out, but they usually need the help of one as coming out of a zone-out on their own would be extremely difficult and taxing

IV) A way to get a Sentinel out of a zone-out is by being calm and stimulating another sense for the Sentinel to stop focusing on the one that they zoned on

About the Sentinel/Guide bond

I) It can sometimes be portrayed/described as a — literal or not — soulmate bond, where the Sentinel and Guide are destined to find and be together

For example the Sentinel finds the Guide’s scent pleasant or their heartbeat grounding. Meanwhile for the Guide, the Sentinel will give them that sense of protection.

III) That ‘soulmate’ or soulmate bond is not mandatory, however in most cases the S/G will still retain a deep connection between the two, connection that can lead to a growing awareness of each other’s location and empathy

III) That bond can be expressed, for example, by the Sentinel knowing the Guide in some sort of sensory profile (= recognize their smell, footsteps, breath pattern… etc), while the Guide can create a mental connection with the Sentinel

IV) That bond, whether platonic/romantic/sexual, can be sealed by a ‘bonding bite’ in some stories, in a similar way to a mating bite in A/B/O