How do I decide what magic/tech can’t do in D&D?

Limits are what make power believable.

Most magic systems and advanced technologies feel flat because they are designed around what they can do, not what they cannot. When something solves every problem, tension disappears. When it works inconsistently or conveniently, trust disappears. Good limits create friction, choice, and consequence.

The goal is not to weaken your system. It is to give it shape.

Start by deciding what problem the system exists to solve.

Every magic system or piece of technology was created in response to something. Scarcity. Violence. Distance. Ignorance. Mortality. Once you know the original problem, you can define what it does well and, just as importantly, what it was never meant to handle.

A healing system designed to treat wounds may not address disease. A teleportation network built for goods might fail with living beings. A prediction engine designed for patterns may break down under human emotion.

Limits feel natural when they come from original intent.

Choose one category the system fundamentally struggles with.

Good systems are asymmetric. They are powerful in one direction and weak in another. Pick a category where the system consistently fails or causes harm. Time. Scale. Precision. Permanence. Ethics. Emotional nuance. Identity. Control.

This should not be a temporary flaw that gets patched later. It should be structural.

Something users work around, fear, or accept as the cost of using it.

If everything is fixable, nothing matters.

Decide what the system cannot do without breaking something else.

Tradeoffs are stronger than hard walls. Instead of saying “it cannot do X,” say “it can do X, but the cost is unacceptable.” Energy drain. Physical damage. Social fallout. Moral compromise. Loss of autonomy. Long-term instability.

This keeps the system tempting without making it dominant. Characters can choose to cross the line, but the line matters.

Make sure the cost hits something characters care about.

Avoid making limits purely technical.

Technical limits are easy to bypass narratively. Emotional and social limits are harder. A system that cannot lie. One that cannot act without consent. One that reveals truth but destroys trust. One that works only in isolation. One that requires community but erodes individuality.

These limits create story instead of obstacles.

Let limitations shape behavior and culture.

If magic cannot resurrect the dead, grief rituals become important. If technology cannot scale cheaply, inequality grows. If power cannot be hidden, secrecy disappears. Limits should change how people live, not just how conflicts resolve.

When limits affect daily life, they stop feeling arbitrary.

This is where visual storytelling helps a lot.

Limits often show up visually before they show up in dialogue. Protective gear. Ritual scars. Restricted spaces. Warning symbols. The way people prepare before using power. Seeing those patterns makes the limitation feel embedded rather than explained.

Being able to test how those constraints look on characters helps catch contradictions early. Tools like Faes AR let you experiment with how magic or tech limitations manifest visually. When the look does not match the rule, something is off. https://faes.ar/

Decide what the system refuses to touch.

This is a subtle but powerful constraint. Some systems simply do not interact with certain things. Maybe magic cannot alter memory. Maybe tech cannot interpret faith. Maybe AI cannot generate intent. These refusals can be philosophical, not mechanical.

Refusal creates mystery without vagueness.

Keep limits consistent even when inconvenient.

The fastest way to ruin a system is to break its limits to save the plot. If the rule bends once, players will expect it to bend again. Instead, let the story bend. Let characters fail. Let them pay the price. Let the world react honestly.

Consistency builds trust. Trust creates tension.

Avoid explaining limits through exposition alone.

Show the limit before you explain it. Let a character try and fail. Let someone warn another and be ignored. Let consequences play out visibly. Explanation should confirm what the audience already suspects, not introduce new rules mid-scene.

Limits feel fair when they are experienced, not announced.

Use limits to force collaboration.

One of the best uses of limitation is making systems incomplete on their own. Magic needs logistics. Tech needs belief. Power needs witnesses. When no single solution works alone, characters have to rely on each other.

This prevents one system from dominating the narrative.

Pressure test your limits.

Ask a simple question. If this limitation did not exist, what would break? If the answer is “nothing important,” the limit is probably decorative. A real limit should change strategy, ethics, or outcome.

If removing the limit simplifies the world, you need it.

Finally, let limits remain unsolved.

Resist the urge to promise future fixes. Not every limitation needs a workaround, upgrade, or prophecy. Some boundaries exist because they always have. Accepting that makes the world feel older and more grounded.

If you want to sanity-check whether your limitations actually read in practice, especially through character behavior and visual cues, tools like Faes AR can help you see whether those constraints feel embodied or theoretical. https://faes.ar/

Power systems feel real when they say no as often as they say yes.

When magic or technology has clear boundaries, meaningful costs, and visible consequences, it stops being a solution engine and starts being part of the world. That is when players stop asking how to exploit it and start asking how to live with it.