Illusions are tricky things to adjudicate in a system which is as flexible as Ars Magica. Questions of adjustments for complexity, accuracy and detail in the conjured illusion all are reasonable however as there is a wide degree of variability in the allowances for complexity in the canonical spells, often the players themselves need to reach their own conclusions (which is generally a potential strength rather than weakness of the system in my opinion, but then I like the banter).
A good question was asked in the forums on “attacking with illusions” and I then started thinking about a more powerful version of a core spell which overloads the target’s senses. Overloading the senses of opponents is one of the easiest spells to leverage.
The Ars Magica rulebook Houses of Hermes: Societies, p68 has a spell called An Enemy Awash in the Pure Sigil of the Magus (CrIm15). By overloading the target’s eyes with visual sensations, this spell can blind the target for 2+ minutes, without using a Perdo requisite to physically “damage” the target. It is not always effective beyond one combat round, but it is still a very good spell. Particularly so because it is not an exceptionally high level spell, nor does it depend on the type of target, and it’s low level makes it potentially good for penetrating magical resistance.
So canonically overloading a sensory organ to the point of failure is very plausible. At level 15 for a Range: Sight spell it is also significantly better than blinding a target with Perdo Corpus which is many magnitudes higher.
Below are versions of that spell to overload many senses of one target, or the visual sense of a group of targets. And most easy to learn for many Magi and it does not permanently damage the target.
An Enemy Immersed in a Sea of Stimulus
Creo Imagonem 25, R: Sight, D: Concentration, T: Part
This spell projects magical species at the target seeking to overload their senses of sight, hearing, and touch. The spell requires no Finesse check to target. The target may be disorientated for up to two minutes after the caster ceases concentrating (see HoH:S 68).
(Base 4, +3 Sight, +1 Concentration, +1 Part)
The effect is adjusted upward by one magnitude for each of hearing and touch, to create an effect which overloads the target’s sense of touch, hearing and sight (from base effect level 2 to base 4).
It is arguable how much more effective the spell effect would be when three senses are overloaded at the same time. In the original spell the target can shut their eyes to only be affected for a round, which seems less plausible for a spell which affects three senses. I suggest that the target is disorientated while the caster concentrates, and given the spell’s level that is not unreasonable.