The casting sigil (in Ars Magica) is a magical effect that is personal to the magus, and persists across all the magi’s spells as an inherent effect. Think of it as a theme or flavour text added to each spell.
It could be considered a variable in-built automatic fingerprint within the magic itself, that may identify the caster.
Sigils can be as strange as the player likes, but would always be present. Ideally the sigil would even be included in the character’s sheet for specific spells. Creating the sigil is as personal as a character name, and should add something to the lore of the character. I like the idea enough that I’d like to see it adopted in other spell casting games; even the mainstream games like DnD could add this without a negative aspect. Of course it might be a tad of a giveaway sometimes (like sound when you’re trying to cast silently), but that should be all part of the glamour.
In the games I’ve played the sigil also scaled with the level of the spell, and potential side effects. It makes sense to me that a powerful spell would also contain a more powerful expression of the magi’s sigil.
I’ve seen some odd stuff as sigils.
- Blood dripping from the hands of the magus. This might be expanded for particularly strong spells to be a full stigmata, or for a weak spell, just the touch of blood on the fingertips.
- The sound and feeling of wind, storms, or thunder; relative to the power of the spell.
- The sound of music, with flutes and lutes for some powers, and drums and horns for others.
- The sound of chimes or discordant gears from a verditius mage, depending on either hurtful or protective magic.
- Shadows become me pronounced, somehow deeper, and other light sources brighter and sharper.
- A minor swell of gravity toward and then away from the magus, where grass might lean inwards and outwards, or powerful trees will sway as the spell takes effect. Doors swing and close.
As other examples, this is a list of a few (stolen) from the official ArM forums. Go read them there too. E.g:
- Maga has “incorporeality” as her casting sigil – her spells appear to make things more translucent, light, or so on.
- A Criamon magus had the sigil of “Enigmatic Runes”, manifesting both in the spell’s effect and on his body. The runes could actually be interpreted by someone with Enigmatic Wisdom, pointing to him and perhaps revealing something.
- A Jerbiton magus’ signature is that things appear to be more idealistic if at all possible; his magic is centered around the Chivalric ideals.
- Musical, Magical Troubador Mercere – urge to sing and dance among those nearby.
- A herbum specialist – flowering plants appear to blossom.
- Verditius swordsmith – brief sting of hot metal on his hands.
- Flambeau engineer – steam forms around caster.
- Flambeau bruiser – hair singes (keeps the hair fairly short).
- Verditius weaver – threads seem to spin out from her casting tools.
The Iron-Bound Tome 