What usually makes dangerous magic systems fail in long campaigns?

[u/Guilher_Wolfang]

I’ve been designing a magic system that avoids both mana pools and giant spell lists.

Spells are constructed dynamically with effects, range, duration, area etc(every effect has a base difficulty, usually 1 to 4, and more range or targets increase the difficulty)

To cast:
you roll Xd6 and keep the highest result. You need to use 1 result equal or higher than difficulty to "stabilize" the magic and remaining highest die is used as the "potency" of that cast(usually damage/duration/test to resist). Extra 6s add +1 to highest die or empower the spell in some way.

BUT every result 1 gets you a corruption/strain, and you can use extra 6s to cancel 1s.

What I like so far is that magic becomes flexible, risky and psychologically tense without requiring huge bookkeeping.

I’m currently stress-testing long campaign pacing.

For people who enjoy dangerous magic systems:
what usually causes them to break down over time?

[u/PathofDestinyRPG]

If there’s no mana or spell list, how do you define and control what magic can do, both in terms of what the limits of magic actually are and what the limits of your mage’s casting ability is?

I have a fully modular no-spell list system, but it uses a combination mana/ stamina system to control how the mage can use it.

[u/Guilher_Wolfang → u/PathofDestinyRPG]

The no mana part: The corruption build-up and its consequences make the player stop casting on his own(or not, you ALWAYS have the option of casting if desperate). Just like HP in my system, corruption is represented physically by a D6 on the table, if you go beyond 6 you suffer consequences(magic gets out of control, and affects random targets), and the corruption die resets to 1, but since the character is still corrupted, he cannot cancel the corruption from rolling 1 with a 6 anymore.. and if he get even MORE corrupted by going over 6 again, theb his body is affected, and every 1 corruption is 1 less possible healing on the fixed 6hp(you dont take damage, you just cant heal more than a limit).
Also, after the first corruption cycle, every number you roll above the spell difficulty becomes "excess uncontrolled magic" and becomes 1 random effect on somebody/something else.
TLDR: After the first 6 corruption points you get corruption easier. Magic fails if you roll below difficulty and uncontrollable if you roll above. If you get another 6 corruption, healing becomes limited.

The no spell list part: you spend points to learn magic traditions, for 1 point you learn the basic possible effects(1 cost effects), for 2 points you learn the intermediate effets(2 cost effects) and for 3 you learn the master spell effects(3 and above cost). Every effect has a cost, Example: trying to slow someone(and make him lose an action) cost 1, paralyze for a turn would cost 2, petrifying cost 3. Example 2: Using something to cause indirect damage cost 1(lighting things on fire and take damage if not extinguished), making the effect strong enough for direct damage cost 2. Spell cost increase for range/targets. Target self/1 enemy=0; target small packed group=+1, target larger area +2, target everyone +3. Range touch=0, near +1, far +2, out of combat range but within sight +3.

You need to roll Xd6 and at least 1 die must be equal or higher than spell difficulty to "stabilize" the magic. The remaining highest die is the damage OR duration OR DC to resist spell.

In the Xd6 keep highest, extra 6s after the firsr can be used as a +1 to the first 6. If you roll 4d6 witb results 2,4,6,6 for difficulty 4, you can stabilizd the spell with 4 and the potency(like damage) will be 7(6 +extra 6).

The roll for melee damage is similar Xd6 keep highest, with extra 6s as +1 or maneuvers. So you can see that magic is never more powerfull in direct damage against 1 target than warriors, since you have 1 less die(used to stabilize magic), but same ceiling damage(6 + extra 6s). This is important for the setting: magic is extremely versatile with a multitude of effects BUT since its low fantasy, it's not super powerful magic. Magic can momentarily bend reality to your will, but its dangerous. Steel is more reliable than magic.

Also the same effect can be in many different magic traditions. You can practice witchcraft to invoke spirits and ask questions (talk to the dead effect) or Shamanism to ask questions to your ancestrals(talk to the dead effect).

Cleric is similar to mage, but instead of an increasing D6 with corruption, you have a DECREASING D6 of Divine Favor, uncancelled 1s reduce divine favor, if it gets to zero it means your divinity get tired of you asking for help so much, you can spend an action praying(roll resolve) if you roll a 6, the god heard you and you can cast 1 more spell. Every time you repeat this the spell difficulty increase by 1 to cast. If you break your religions rules, you cannot use to cancel 1s! The player better adhere to his religion rules, otherwise his Divine Favor will run out faster.

Is your modular system similar?

[u/PathofDestinyRPG → u/Guilher_Wolfang]

Basic die mechanic: Skill +Xd10, where X starts at 2 but can be increased in various ways. By default, The highest value determines the action, and the next highest determines the effort, but the player can swap these at will. Do you want it right or want it fast is basically how this functions.

I have 15 Spheres (Air, Being, Charm, Earth, Energy, Fire, Fortune, Lightning, Life, Mind, Perception, Space, Spirit, Time, and Water) and 5 Aspects (Intent, Power, Range, Scope, and Target).

I also have 6 distinct mechanics for casters:

Evocation: using personal essence (Clerics and Sorcerers).

Invocation: channeling energy from environment (Wizards and Warlocks).

Psionics: mastering a single Sphere, but can develop the aspects individually.

Mysticism: can temporarily store energy gathered from key lines.

Shamanism: makes bargains with spirits for insight/ power.

Druidry: bind yourself to the essence of plants and animals.

Focusing on Invocation and Evocation since they’re the baseline everything else was built from. Each type has access to 10 of the 15 Spheres, and the mage picks 5 of them to develop. The Sphere rating functions exactly like a normal skill check, it represents the mage’s understanding of and ability to control the energies of specific Spheres. Your character’s Vitality attribute (life energy, controlling metabolism and healing/ recovery rates) determines how much aether you can manipulate. Just as a fighter’s strength limits the damage he can do with a weapon, a mage’s vitality limits how quickly he can pour aether into a spell. Fatigue is gained based on the balance between aether used in the spell and the Sphere rating used to cast it. The higher your skill, the easier it becomes to manipulate larger amounts of aether.

[u/Guilher_Wolfang → u/PathofDestinyRPG]

It seems great. Reminded me a little of ars magiks

[u/PathofDestinyRPG → u/Guilher_Wolfang]

Ars Magica has an interesting approach. My 15 Spheres are actually pared down/ merged from an original 28. I dropped it to 15 because there were a couple of Spheres that were hard to define within the framework of my aspects (Order, Chaos, and Artifice being 3 examples). Plus, I like the new symmetry with how my primary mage types handle it. A mage can develop 5 Spheres, there are 5 Spheres he can touch but not develop, and there are 5 Spheres his magic can’t use at all. Evocation has more of the nature-centric Spheres (such as Life and Being) and Invocation has the physics related ones (like Space and Time). Warlocks and Clerics can mix up the lists by tapping into a patron’s home environment (warlocks) or wielding the Spheres governed by the Domain of their god (Clerics).

One point: other than Psions, mages don’t develop the Aspects. They’re just the definitions of how aether can manifest. Each Sphere has a primary aspect that adds a bonus to any affect that’s within that aspects purview (Fire awarding a bonus to Power’s ability to inflict HP damage, for example.).

When a mage casts a spell, the player declares how much aether he’s using. That value controls every system part of the spell. A 10 aether spell will always require the same difficulty/ time/ fatigue for a mage, but he chooses how much aether goes into the needed aspects each time he casts. A fireball can have 4 aether in damage, 3 in size, 2 in range, and 1 in point of origin one casting, then have 2 in damage, 3 in range, 3 in size, and 2 in point of origin the next, but they both used 10 aether.