Fast casting against another wizard in Ars Magica

One of those forum conversations that leads into a brief explanation of how the game mechanics resolve magic… The Mirror of Opposition spell reverses the effect of a spell, but not the target. So a spell to hurt a person might help them instead. It is a very interesting spell because it relies on so many of the meta-magic layers in Ars Magica, primarily around Muto Vim spells, but there are compounding questions in the details.

Pyrale wrote: Another question regarding spell manipulation : Supposing I see someone starts casting, and I decide to cast a mirror of opposition on his spell. Does my spell have to pierce the caster’s defenses ?

If not, do I have a window of opportunity if the spell has no time of travel, or can I only cast it on projectiles ?

My 2c which might be dodgy… I think you can cast it on anything, and the SG gets to decide what it does.

  • First you need to use the rules for identifying what Form the spell is, because Mirror of Opposition is different for each Form, but I guess you might know if the caster had previously been shooting away with missile spells and just assume you’re correct if your perception Check failed. The Perception check isn’t going to slow down the rest.
    … Perception + Awareness + roll vs. 15 – (effect mag). If the opposing caster has silent/subtle magic/deft magic it gets a lot harder.
  • Then if you are not cooperating with the other caster (fair assumption) you need to fast-cast the MoO:(form), as per p.159 of Ars about not being able to intercept the spell quickly enough. Its basically a -10 to casting roll with 2x extra botch dice, and you need the fast-cast Mastery option for the MoO spell.
  • Then your Penetration total for your casting roll (which includes that -10 mod) must beat the other caster’s Penetration total
    (i.e. spell CT + roll – Spell level + Pen ability vs same from the other guy).
  • The rules imply that you don’t need to penetrate the caster’s parma which is great, although if they were casting a spell with Range: Personal upon themselves I’d argue that you’d also need to penetrate their Parma for it to work too (?).
  • The caster must be in range of your MoO spell too (voice), unless you’ve got a funky version or using an Intangible Tunnel and an AC.
  • I don’t know what happens if they are fast-casting a mastered spell, but I think you still could fast cast to intercept and alter it (?).
  • You can’t alter Spont spells with MuVi which is a bugger but it makes sense why.

Easy! However…

  • If the first spell was fast-cast then the second magus can fast-cast one to defend/intercept, but it should come back to speed (point made here). Essentially the magic system seeks to avoid situations where magi just fast-cast-BLAST their way through all encounters.
  • As MoO and many other Muto Vim spells do not work against Spont magic, and also typically must penetrate against the target spell, and also usually only affect half their level, not many wizards are able to Spont cast Muto Vim spells in defence. It is possible, but very unlikely.

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Spells to strengthen the mind and resist other Mentem spells?

Can a spell make a mind more resistant to coercion? Or more resistant to magical manipulation? I’d say yes, so this post is a discussion of the points to why, and a few spells to demonstrate potential approaches.

A Perdo Mentem spell can dramatically increase the chance of manipulating somebody, then a Rego effect could allow them to not change their mind, or perhaps a Creo effect could make the mind more resilient or logical. A spell can probably artificially strengthen a target’s resolve and willpower.

This might come into play mechanically by altering the target’s personality traits, or describing a change in behaviour in a more abstract manner just like the cannon spell from the Ars Magica main rulebook Trust of the Childlike Faith (a PeMe spell where the target will believe almost any passable lie).

The Dogged Will

Rego Mentem 25, R: Voice, D: Sun, T: Individual

The target finds it impossible to change their opinions and beliefs for the duration of the spell. Only the intervention of a more powerful supernatural effect will allow the target’s views to be changed.

(Base 5, +2 Voice, +2 Sun)

But will that add more defence against another spell when the second effect is active at the same time as the first, and is lower level, and also has a similar effect? Yes, but it wouldn’t protect against manipulation of memories or state of mind, potentially leading to a person understanding an alternative point of view but unable to change their specific opinions or core beliefs.

It is perhaps similar to when two similar spells wish to perform directly contradictory actions, such as to change a targets shape. Assuming equal penetration; transforming a human into a cat at level 25 or a bird at level 30. The level 30 effect will be dominant, but the cat effect is still there underneath. If the bird effect is prematurely ended then the target becomes a cat. What fun!

I think there is also a difference between improving the mind’s capacity for reasoning, enhancing the mind’s capability to resist being changed, and forcing the mind to stay the same; Creo vs Rego in terms of Arts. That presents an alternate Creo spell.

Enhancement of Logic and Reason

Creo Mentem 25, R: Voice, D: Sun, T: Individual

The target’s mind is better able to operate logically, reason more soundly, and ignore some of its emotional preconceived notions. This may grant bonuses to ability rolls, willpower checks, or alter personality traits favourably in those circumstances.

(Base 5, +2 Voice, +2 Sun)

And aversion for a council chamber or meeting hall, because that is where logic is needed.

Solar of Enhanced Logic and Reason

Creo Mentem 35, R: Voice, D: Sun, T: Individual

All targets in the affected room are better able to operate logically, reason more soundly, and ignore some of their emotional preconceived notions. This may grant bonuses to ability rolls, willpower checks, or alter personality traits favourably in those circumstances.

(Base 5, +2 Voice, +2 Sun, +2 Room)

Perhaps these effects haven’t been considered all that useful for magi due to Parma Magica resisting the effects, andthe laws of casting upon others? Perhaps useful as an invested device for a mundane sheriff or knight. There are Rego Vim spells to prohibit teleportation spells, scrying spells, or intangible tunnel spells, so it’s just as plausible to ward against mental spells. The effect being resisted will need to be specific.

Impede the Dominating Will

Perdo Mentem Gen, R: Touch, D: Sun, T: Individual

The target’s mind is protected against Mentem spells or supernatural effects seeking to issue instructions and commands, or directly alter the target’s behaviour; requiring any opposing spell to exceed (level of this spell +5 + stress dice (no botch)). It has no effect on other spells, or similar Mentem spells which alter memories in the target.

(Base Gen, +1 Touch, +2 Sun)

This could be useful for a Magus and/or Familiar if enchanted into a familiar link, to allow for constant protection with no ongoing warping. Then for others, as:

Impede the Dominating Will, Encircled

Perdo Mentem Gen, R: Touch, D: Ring, T: Circle

The target’s mind is protected against Mentem spells or supernatural effects seeking to issue instructions and commands, or directly alter the target’s behaviour; requiring any opposing spell to exceed (level of this spell +5 + stress dice (no botch)). It has no effect on other spells, or similar Mentem spells which alter memories in the target.

(Base Gen, +1 Touch, +2 Ring)

The PeVi baseline is from Ars Magica core rules, as demonstrated in the anti-teleportation spells from TME p109. These and many more new spells for Ars Magica in my grimoire of spells.