Spells for Carcosa, or, The Fungi From Yuggoth

The Last of Us

Spells are alien lifeforms native to the jale moon Yuggoth. They exist alternately as memetic information and fungal growths. Spells are not intelligent, but they have evolved a symbiotic relationship with intelligent beings.

In its memetic form, a spell can be encoded as writing, numbers, images, musical tones or many other formats. When an intelligent creature memorises the spell, it grows as a fungus inside their brain.
At the host's command, the spell is ejected from their brain through the nasal cavity and becomes pure magical energy. The actual effects of the spell are, in biological terms, its spores. By proving itself useful to its host, the spell ensures that it will be copied again and again.

Dedicated magic-users undergo training to increase their spellcasting capacity - literally creating cavities in their brains for the fungus to take root.

A O Spare

Rules
- The first time you try to memorise a particular spell, make a Will/Wisdom save. On a success, your brain is incompatible with the spell and you will never be able to learn it.
- You cannot memorise multiple copies of the same spell. Either you have it or you don't. After you cast a spell, you can't memorise it again until the next day.
- Once you have memorised a spell, you can only get rid of it by casting it. 
- When you eat the brain of another magic-user, their memorised spells will be transferred to you. Any spells they recently cast (within the last 10 minutes or so) have a 50% chance of being transferred as well.
- Spells cannot be written in cipher or otherwise concealed by translation. A spell is always a spell no matter what form it has been transcribed into.

Spell Slots
- All PCs begin with spell slots = 0. Gain spell slots through whatever system of character advancement you are using.
- Anyone can memorise any number of spells, regardless of their spell slots.
- When you cast a spell, if the number of spells in your brain exceeds your spell slots, you must roll on the Spell Misfire Table. Roll one die for each spell that exceeds your spell slots, and take the highest die.

Spell Misfire (d10)
1. Spell is cast successfully.
2. Spell works only for a moment, or is at half strength.
3. Spell refuses to come out. Choke on spores for 1 round, but the spell stays in your brain.
4. Spell fuses with another spell in your brain, creating a new hybrid spell which is cast immediately.
5. Spell is not cast, but instead copied into the brains of everyone else in the area.
6. Spell fails and is lost.
7. You give birth through your forehead to a child, half-spell and half-human. Has the same hit dice as you and abilities based on the spell's effects. Roll reaction to see how it regards you.
8. Spell succeeds, but comes out through your face. Take 1d10 damage and permanent facial scarring.
9. Spell possesses your body permanently, while your spirit becomes a spell.
10. Your head explodes as the spell is cast with incredible potency.