I'm looking to invent a spell that would get a Magus inside a windowless /doorless room that he can see. The idea would be that a magus could have an easy way in and out of a secret room.
At first I was thinking of a MuTe spell that changed stone to mist for a Concentration duration.
Now I'm thinking of a ReCo spell, where the Magus touches the wall, and then appears on the other side. My question is, is this basically "Leap of Homecoming," or is the spell of a lower magnitude?
Guidelines on page 135 say that Level 10 transports the target up to 5 paces. But since he can't see the other side of the wall, I'm guessing he'd have to use the Level 35 guideline (arcane connection).
Prying Eyes (Intelligo Imaginem 5)
Arm5 (Page 144)
This lets you see into a room if you touch one of the walls/door
ReCo10 is enough. Take a look at Seven-League Stride for clarity. You don't need the distance of the level-35 base. You just need to know your arrival location, which can be via Arcane Connection if you can't see it.
As with many things Ars Magica, there are multiple ways to solve that problem.
Getting into the room could be making the stone intangible, making yourself intangible, teleporting or creating a door by magic. There's probably other options, too.
For teleportation, you need to identify the target location. This could be via Arcane Connection, or it could be via one of many ways to sense the inside of the room. You could use Prying Eyes. You could muto the wall to make it transparent. Again, there's probably other options too.
While the Prying Eyes / Wizard's Leap approach is probably one of the lower level options, the exact approach taken is also going to depend to a degree on the strengths and weaknesses of the magus.
I guess my question is:
Does the rock wall that the magus is touching count as an arcane connection to itself? So the magus can simply touch the wall, and pop over to the other side?
That's going to vary enough that the casting magus is going to get infuriated at least once.
One of the key tenets of Ars Magica is that it relies on objects and their relationship to other objects over geometry. As such, whether a wall is a valid arcane connection to the adjoining room will vary based on the wall.
Essentially, the question is 'is the wall validly part of the room beyond?'
Imagine you're standing next to the wall of a one-room cottage. The wall is clearly part of the cottage, so if you wanted to teleport inside the cottage then touching the wall to get in would be fine.
But if you're already inside the cottage, there isn't a valid room on the other side of the wall. You're in the valid room. So using such a spell to teleport to the other side of the wall will fail, because you've got no related location to go to. At best you'll teleport to somewhere more auspicious / sigil-appropriate within the room you're already in.
This is why some form of scrying your destination first is a really good idea. Just be aware that any scrying spell that relies on a room target (e.g. Prying Eyes) is going to have the exact same problem.
This is why most of the published 'I want to get through a wall' spells tend to be spells cast either on the caster directly or on the wall directly. Both of these are guaranteed to exist, regardless of which side of the wall you're on. Muto-ing the wall so a person can simply walk through it neatly sidesteps questions about what is on the other side of the wall and how it relates to the wall itself.
The other alternative is to introduce geometry into your spell-casting, then use target:Line or similar. The down-side here is this isn't standard hermetic magic, so some mystery cult initiation or similar will be required. See 'The Mysteries: Revised Edition' for details on geometry and spell-casting.
The Magus could also PeIm or ReIm a section of the wall's image so that they can see clearly through it. Then target the spot they can see. There was a Tremere spell for this from memory (but isn't that almost always true).
I don't think that's actually the case. You should be able to simply use a ReCo 10 effect to move yourself 5 paces away on the other side of the wall. You don't need to know anything about the location you end up at, as that isn't the target of the spell. You are the target of the spell.
Of course, it would still be wise to scry beforehand to check you aren't going to end up inside the wall, in a pit of snakes, etc.
I'm not sure you could teleport inside a wall. A person co-existing with a wall isn't a natural state for a person (or a wall) to be in, so it fails the requirements of Rego. Even people buried/trapped in foundations don't literally co-exist with the stonework. Spellcasting botches notwithstanding, of course.
Strictly, you can't teleport into a location underwater either, as there is water there. (Or into open space as that is arguably full of air --- although perhaps not under the medieval model).
Presumably, the argument is that you can teleport under water and either displace or wrap around the water. So if you try to teleport into a wall you should likewise displace or wrap around the stone. Which is generally fatal, and a bad idea. Although, of course, potentially you could have the right MuCo effect to nonetheless survive.
Hm... doesn't the mystic Geometry "line" range specifically allow you to have ranges through walls? (...Vacation's Parma - I'm away from my books ATM).
Should that be "Jerbiton's Parma"? 