Δelta: Key and Lock Arts

The purpose of a wall is deny access to a location, the purpose of a tunnel is to allow access to a location, the purpose of a door is to do both. Ironically many of the thaumaturges who devote themselves the most to doors must blind themselves to this fact if they want to practice the secret Arts of Key and Lock.

To iterate, a door is meant to be semi-permeable. If it allows everything through or allows nothing through it's not a good door. At the very least they should be easily let people pass, but keep temperature and spirits on one side of the threshold. A door can be more selective in what it allows through with other methods like locks and guards and riddles. A door can be less selective by other methods such as being light enough that the wind can open it. But in any case, it is paramount that it both allows and denies. Doors are not the only domain where such a pattern is observed. Your skin both traps heat within you and sweats it out to keep that you need boil or freeze. Rope is tied in knots that are both sturdy and easy to undo, so that sails are bound or unfurled in response to the winds. Communities accept and reject people based an numberless traits, thereby establishing their identity. Law tells what people can and cannot do, theoretically to support justice. People accept and discard countless things and thereby define who they are. Differentiating things is vital for anything to survive and make sense of the world and have free will, and is the ability that is sacrificed to the Key and the Lock.

Key and Lock Arts are a simple metaphysical exchange. It's a promise that when presented with a specific 'yes' or a 'no' question your answer will always be the same regardless of circumstance, but in exchange the 'yes' or 'no' becomes a 'YES!' or a 'NO!' that the universe is compelled to listen to. A Key adept of doors can enter any building but cannot close the path behind them. A Lock adept of doors can barricade themselves inside any building but trapped inside once they do so. This begs the question of what happens when a Key adept tries to open a door that a Lock adept is keeping closed, for that I'll define a scale to measure magical might by.

Unstoppable Force vs Immovable Object:

Some magics are stronger then others. Some arcane bindings can only hold back ghosts, while other cannot be breached by the gods. Magical forces that can break through barriers also vary from being able to shatter weak barriers to forcing all doors to open before them. Here are some rules for how to rule that.

In a scenario where two magical Forces are pushing against each other. Figure out which rank of power each Force has, the one with the higher rank wins. If they have the same rank, the the defending Force wins, unless the attacking force can find a edge against (such a dragon's True Name) or an opening (such as a momentary lapse of concentration) in the defending Force. If neither is the clear aggressor, the Forces are stuck in a grapple until something changes (such as one side growing tired and leaving an opening for the other). Finding a edge or an opening can be thought of as lowering an opponent's rank down one.

It is known that casting magic is an act of Will, so enchantments are ranked by what is the strongest Will that cannot break from it. Note that offensive and defensive ranks in a given situation do not have to match up. Demons can often be Trivially held back with a simple gesture while being capable of Strong possession. Likewise a human with a good head on their shoulders and a Strong heart is unlikely to be capable of even Trivial possession.

1. Trivial- Cannot be overcome by the soulless. Fey, figments, egregores, sorcerers who sold away their heart.
2. Weak- Cannot be overcome by Wills that lose sight of themselves. Ghosts, directionless people, most household items, broken spirits.
3. Strong- Cannot be overcome by Wills that think they understand themselves. Steady hearts, desperate souls, houses that have lived a hundred years, rivers, wild horses, mere insects.
4. Great-Cannot be overcome by Wills that know themselves. Saints, Dragons, Oceans.

This ruleset is MOSAIC Strict and arguably unnecessary because you could probably get the same result by just using the everyday definitions of Trivial/Weak/Strong/Great to describe how powerful magics are.

🔑Key Arts:

The Oath Unbarred:

Choose a domain in which things there is an 'open' and 'closed's state, swear an oath to always keep that thing open. If you ever 'close' anything in this domain, lose this template.

• You can open anything in your chosen domain with Weak power, keeping it magically opened for as long as you keep The Oath Unbarred or the magic is broken. 
• You can dispel this magic with a thought.

Ritual of Unlocking:

Take something that keeps you safe and secured and lose it to power an Oath Unbarred. If you ever regain this anchor, lose this template.

• You can open anything in your domain with Strong power, and do so with barely a glance. 
• You can dispel this magic with a few minutes of concentration. 
• Closing in your domain becomes difficult, like pulling out nails with your bare hands or lifting a stone block. 

Key:

Forget the anchor that you sacrificed in the Ritual of Unlocking. You can not lose this template or regain the anchor.

• You can open anything in your domain with Great power. 
• You cannot dispel this magic.
• You cannot close anything in your domain, no matter how much you try.

🔒Lock Arts:

The Oath Contained:

Choose a domain in which things there is an 'open' and 'closed's state, swear an oath to always keep that thing closed. If you ever 'open' anthing in this domain, lose this template.

• You can close anything in your domain with Weak power, keeping it magically sealed for as long as you keep The Oath Contained or or the magic is broken. 
• You can dispel this magic with a thought.

Ritual of Sealing:

Take something that you treasure and make hide it in the Ritual of Sealing. If anyone accesses your treasure, lose this template.

• You can close anything in your domain with Strong power.  
• You can dispel this magic with a few minutes concentration.
• Opening in your domain becomes difficult, like pulling out nails with your bare hands or lifting a stone block.

Lock:

Forget the treasure you hid during the Ritual of Sealing. You can not lose this template, or have your treasure.

• You can close anything in your domain with Great power. 
• You cannot dispel this magic.
• You can not open anything in your domain, no matter how much you try. 

Domains:

You can take the same Key or Lock Arts multiple times by taking the Art in different domains. A domain can be practically anything as long as the actions of 'opening' or allowing and 'closing' or denying can be applied to it. However make sure to keep it consistent. When a player takes an oath Unbarred or Contained make sure to come to an agreement with GM on what that oath applies to and write it down somewhere for future reference. Here are some examples.

• Doors:This one is fairly straight forward. Key adepts are able to open doors with it, Lock adepts can keep them shut.
• Specific Doors: The domain can be as narrow as one door. This is actually more common then choosing doors in general, a lot of Lock adepts are dedicated to protecting one vault from intruders. The more secure prisons of the world are enchanted to prevent inmates from using Key Arts against the specific doors that hold them. 
• Truth: As a Key Art everyone must answer your questions truthfully, but you must answer their questions truthfully as well. As a Lock Art no one can force an answer out of you, but you can't force an answer out of someone either.
• Skin: As a Key Art allows you to cut with ease, making you able to leave terrible wounds with a dull knife or blade of grass but leaving you vulnerable of the same. As a Lock Art you can make skin impermeable or fuse wounds shut which can be bad if you need to sweat off excessive heat.
• Dreams: Naturally one's dreamworld has a semipermeable membrane connecting it to the rest of the dreamscape. Removing the membrane allows you to freely shift the dreams of others but leaves you exposed to astral parasites, while closing it off completely defending you from outside influences but leaves you spiritually inert.
• Contract: Everyone knows what magical contracts are, two sides form an agreement and if one breaks their end then they start coughing up blood and the other side knows about it immediately, this is a classic Lock Art. The related Key Art allows you to break the Contract without the blood or notification. Authoritys hate them, Oathbreakers get axed even more immediately then Orbseekers.
• Death: You can open yourself to death, this means you will die more easily but making it easier for you to come back as a ghost. You can close yourself to death, not preventing yourself from dying but preventing your soul from leaving the body, this is an important step on the road to lichdom.
• Wood Joints: In the east there is a tradition of mage wrought carpentry, where structures are kept together by Lock Arts, creating structures that easy to erect but you need to trust the adept to keep it stable. Often the Lock mage in question is killed and buried in the building to ensure it's integrety.

Edges and Opennings of the Arts:

While the segnificance of the sacrifice is the source of power in Key and Lock Arts, there are other factors that can sway the the forces one way or another when the strength of two Arts are otherwise evenly matched.

• Domain Complexity: Simpler domains trump more complicated or specific ones, becouse exceptions go against the principle of inflexible law that this sorcery relies on. A Key Art with the domain "all doors" will break through a Lock Art with the domain "this specific vault door". A Key Adept with the domain "truth spoken within a court room" is weaker then a Lock Art of "truth" in general. "Everything" is the simplist and most powerful domain, but no one is known to have successfully preformed an oath with it.
• Time: The older a threshold working is the stronger it is, becouse each time an adept gives the same answer to the question they swore on the more that answer gets reinforced.
• Decay: Entrpy gets all things eventually. This magic will be passively maintained as long as the adept lives but once they truly gone from this world, it will rot ever so slowely over the course of centuries.

This ruleset is MOSAIC Strict if you include the Unstoppable Force vs Immovable Object rules, otherwise it's MOSIC.

Discussion:

I've been picking at this post for at least half a year, and have been mulling over this concept for around a year, but probably longer. The influences for this subsystem consist of the Knock principle in Cultist Simulator, Arnold K's Door Wizard, my CompSci classes and a character one of my friends back in high school made up. The character was a robot that opened doors but could not conceive of and/or fell into existential dread over the idea of closing them, his name was Doorbot. Also shout out to a special someone who willingly discussed if Key adepts can rip pieces of paper or not.

Actually I started writing this post shortly after the time that the Pyromancy Delta dropped. The clever idea I had at the time was that there would be separate Key and Lock delta trees that would eventually merge into a a Thresholds tree that is a synthesis of the two. To gain the Threshold templates you would also have to lose Key and Lock abilities. Also lower ranks were going to be almost mundane roguish abilities that would eventually give way to more and more supernatural ones. Also I wanted it to follow a 'cops and robbers' theme where both Key and Lock deltas have abilities that make sense on both sides of the law. I didn't get far with this plan because it turned out to much for my tiny brain to handle, so this sat in drafts until it occurred to me to take the "open any door, but you cannot close them" template and just expand that into it's own thing.

I'm happy with how this system turned out. Like always I end up writing an elaborate magic system that has interesting setting implications but don't house it in a specific setting where those implications can be explored. I really need to make a setting and stick with it long enough to get something cool out of it. 

Edit: 6/13/2024

Made a few minor edits here and there. Reworded the requirements for each template. Changed a word in the UF v IO section from "key" to "edge" to not be as confusing. Added the Edges and Opennings section, becouse I got new thoughts on the system after some time. Domain Complexity and Time as edges are written the way they are to encourage more inconvient Domains that meaningfully impare your ability to interact with the world like a normal person. I am half considering rewriting Key and Lock Arts to not use the UF v IO measuring stick I wrote and instead be based on these sorts of entirely diegetic considerations. Decay as a possible openning becouse nothing is eternal.