I'm just about to start playing in a new Ars Magica campaign, and the first story arc is going to focus on the establishment of a brand new covenant, in the Lake District of northern England. I'd looked at learning the CrTe spell which lets you create a stone tower, but I was wondering how you'd go about making a ReTe spell which would excavate a cave system in a natural cliff face.
My PC has the Elemental Magic virtue (so adding additional elemental requistes doesn't increase the magnitude), and so one option which has occured would be to find a natural system of limestone caves with a stream in them, and use a ReTe(Aq) type spell to direct the natural water flow to sculpt out the caves for us.
My two big questions at the moment are: 1) Does this qualify as controlling stone in an slightly unnatural manner (Base 2) or a a very unnatural manner (Base 3)? Manipulating a stream (if I went with that option) would seem to be Base 4 (control a liquid in a forceful but calm way). 2) How do I incorporate the size of the cave into the spell? Do I work off the base Individual for Terram of 1 cubic pace of stone, and if so, how do I increase this for a Terram spell (presumably Room and Structure both apply very nicely to existing caves; could I raise the magnitude to Structure and make a nice big cave system that way?).
Essentially, can anyone clarify exactly how you'd use Rego Terram to make a habitable cave system, either from solid rock or by enchancing an existing cave system?
Many thanks in advance.