Not certain if this is answered in canon. I don't have all the books.
But a traveling magi, in hostile country, sets up camp at night. What are the easiest/most efficient temporary fortifications to her camp can the magus cast?
A Sun, or Moon duration Mystic Tower has a higher level than the momentary ritual.
Also, the magus probably doesn't want to leave fortifications behind, for the enemy, once they move on. How would you remove the camp in the morning ?
Any version of "Wall of protecting stone" possibly with a magnitude added to create 250 paces of wall lengrth instead of 25.
Any ReTe spell to raise an earthwork. This would need to be demolished by magic in the morning.
A circle ward against bodies and one against animals. wards are especially useful if you travel with a small group of followers.
A Broch In A Pinch, CrTe 25
Touch, Sun, Ind
(Base 3, +1 Touch, +2 Sun +1 Design +2 Size)
The spell conjures a broch. A broch is a very robust, slightly conical stone dwelling. Large brochs can be 10+ paces tall and have complex internal architecture. Te broch created by the spell is smaller and is made entirely of stone. The walls are circular, 3 paces thick at the base, and get somewhat thinner to form a dome at the top.The internal area is a circular space 5 paces across, and approximately 5 paces tall at the center. There is one small entrance and, and there are no windows.
Conjuration Of The Hasty Hut, CrTe(He) 10
Touch, Sun, Ind
(Base 1, +1 Touch, +2 Sun, +1 Design, +1 Requisute)
The spell creates a clay hut with a simple, circular clay wall about half a pace thick, and an interior space about 2 paces across. The hut has a thatched roof but is only 1 pace tall, the entrance being barely large enough for a person to crawl in. The spell is intended to be used with Perdo Terram effects that destroy dirt to create more space within the hut. These are usually manageable even with spontaneous magic.
A Hut That Isn't
This is an effect created by two spells:
Building The Stoneless Walls, ReAq(Au) 25
Touch, Circle, Ring
(Base 5, +1 Touch, +2 Ring, +1 Requisite)
The spell creates a dome shielded from rain and wind by invisible forces.
Painting the Stoneless Walls, CrIm 5
Touch, Circle, Ring
(Base 1, +1 Touch, +2 Ring, +1 Size)
Creates an illusionary dome that mimics the terrain around the dome. It does not attempt to copy what actually should be in its place, it simply creates motionless imagery which, from the distance, appears to be part of the landscape. Upon close inspection (from a few steps), it's obviously fake.
Considering that ward against the rain has no Aq prerequisite, I don't think you'd need the Aq for this.
If you are good enough at leap of the homecoming grab an AC from the location you have arrived at, leap home for a good night sleep then leap back in the morning.
Just make sure to leave your clothes and supplies in a safe dry place while you are home sleeping...