Corruption Magic for Cairn.

What can I say? I like a magic system that counts up rather than down.

Let me explain.

5e has spell slots. You start out with X slots per level, and end the day with basically X-(spells cast of that level). But that is SO predictable, and isn't magic meant to be anything but?

When a sorcerer in my game draws on the magic in their blood or a wizard bends reality through sheer nerdiness, I want it to feel both powerful and dangerous as all hell to do so.

That's why I can't stop thinking about Symbaroum's casting mechanics. It is far from a perfect game, but the concept of corruption has stayed with me.

Rather than losing spell slots, the use of magic incur corruption. If corruption exceeds "Tough", which is the game's constitution equivalent, the character is turned into a monster. Halfway to becoming a monster the character also gains a visible mark of their corruption. There are also various mystical traditions that can help the character mitigate corruption. 

What I love about this is that the corruption gained for casting spells was variable, meaning you rolled a d4 for each spell you cast. This created an element of risk to every spell, forcing characters to not just wonder if they might need a spell slot later, but to wonder if attempting to cast when at high corruption is even worth it. 

However, its not all good. The corruption section is fairly wordy, and introduces a ton of complexity to the game. You have to manage both permanent (gained for learning spells or gaining marks of corruption) and temporary (for casting spells) corruption. Plus, those traditions were basically just added flavor, and had almost identical mechanics. 

So what about a rules lite version? And how about I make it for Cairn? And what if there is some element of randomness to what happens if you get too much corruption? And what if I threw in a few spells too?

(I won't deny the Thaumalus section was heavily inspired by the Dooms of the Goblin Laws of Gaming wizard)

Well, it's below. Let me know what you think. 

As text:

SPELLCASTING

Spellbooks, scrolls and other magical items incur a cost of corruption measured in d6’s specified by each spell or magic item.

If a character rolls the same value on more than one d6 in their corruption cost or their corruption total exceeds their presence, roll Thaumalus and reduce corruption by the amount rolled. Characters still gain corruption when multiples are rolled. May roll multiple thaumalus’ at one time.

Thaumalus (2d6)

2 transformed. Give player sheet to DM.

3 lose one magic item.

4 HP to 0

5 cannot use magic for 1d4 days.

6 displacement. 1d4 inventory items disappear.

7 weakened. lose Cd4 Body.

8 severe frostbite or burns.

9 all creatures in 20 ft gain 3d6 corruption

10 Will maximum reduced by 1d4.

11 DM gives you a new conviction.

12 spell enhanced. Corruption to 0.

Mystical Traditions create items that can mitigate corruption. If in possession of items from more than one school, test Will 18 or lose them both.

 - Sorcerous Wand: Whenever you roll a 1 or a 4 on a corruption roll, you may instead inflict that corruption on a creature you can see.

 - Theurgical Channel: Spend an hour sanctifying this relic, religious text or other item associated with your deity. When you cast a spell, you can draw on the power stored in this item to cast it for Cd2 corruption. You must spend another hour sanctifying this item again before you can use it.

 - Witch’s Pact: when you experience a Thaumalus, you may choose which result you experience. Replace that result with “physical deformity” for all future rolls.

 - Arcanist’s Tome: Covered in arcane runes. Each time you use a spell, choose one of the corruption dice you roll. If that dice rolls a 1, you capture the energy of the spell in your runes, and may cast it again today for free.

Sample Spellbooks:

Stoneshape Cx5 ft line - a stream of stone flies from your outstretched hands, bonding permanently to anyone and anything it hits.

Sunder - a clear sound rings out as you break one non-ritual magical effect.

Shadowed Track - choose a creature. Their trail becomes illuminated by shadow, only disappearing if they cross running water.

Sensory Parasite: Choose one: sight, sound or speech. C creatures within 10 feet must make a constitution saving throw or lose that sense for 1d4 rounds. You gain advantage on all checks using that sense for the same duration.

Rise - Flesh and bone knit themselves back together at your beckoning into a creature with C Hit Dice. What is made by this spell will obey your command before sinking back into the murk in 5 minutes, unless you fail the spellcasting test, at which point it will turn on you.

Cinder 30 line - your outstretched hand conjures a burning firestorm of coals, dealing Cd6 damage to all in its path.

Upwell - choose seawater, freshwater, hot spring or mud. The ground breaks as a spring of your chosen substance shoots 20 feet into the air.

Witch Sight - for C mins, you see lies and the core motivations of all around you.