Here are some charged devices for sailors and marines; a portable wind, and a magical auger. In the write-up there is the spell effect using common Ars Magica notation and also any enchanted device modifications which might be needed.
Charged devices are better when they are kept low level so that the excess magic can create more of them in a single season – so each effect is basic. More dramatic spells are plausible but would result in less uses.
For example: a junior Magus might be able to generate a lab total around 20 in arts which they have some passing knowledge but no specialisation. (Int 2, Aura 5, Form 4, Tech 4, Magic Theory 3, shape and materials bonus 2). A junior specialist using their chosen arts will be able to generate around a level 25-40 lab total, depending on their arts and if they have an applicable magical focus.
This means a season creating a charged device might grant a few uses, but then working from the lab text created in the previous season creates far more uses. Very useful, especially if the characters can purchase the lab text instead of creating it, or if the work can be repeated by an apprentice.
While knots in string which capture the wind are the traditional folk witch style, a hermetic magus might make use of the shape and materials bonuses to use a fan (+3) or sail (+6) bonus to an lesser device.
A Creo Auram 15 lab total isn’t a high level, especially if a few seasons would be spent. It seems something which an apprentice might even be able to construct in their later years and requires no vis investment.
Captain’s Tiny Sail – this miniature sail contains a spell to summon a normal wind. By turning the sails facing the direction of the wind may be altered.
Summon the Unbound Wind
Creo Auram 10, R: Sight, D: Concentration, T: Individual
This spell summons a normal light wind which blows in a direction controlled by the caster.
(Base 2, +3 Sight, +1 Conc)
Final device level 15 (+5 levels for device maintains Conc)
Woodworker’s Tiny Twigs – these small twigs are each enchanted with a single effect which causes warping and damage to any wooden item, either living or dead. To active the holder targets the device to be affected and snaps them between thumb and finger.
Wrath of Turned Wood
Rego Herbam 10, R: Voice, D: Momentary, T: Part
This spell twists and tears at wooden items, which may warp them beyond use or break them; emulating the changes a disgruntled woodworker could inflict. Chairs are broken, walls holed, and boats ruined. Many successive castings may be required to inflict major damage.
(Base 3, +2 Voice, +1 Part)
The target was specifically chosen as to allow part of a greater object to be affected, such as the hull of a ship.
A slightly odd spell for combative purposes, but one which might have mundane applications is conjuring a large volume of clay for just long enough to impact a battle. The same very simple spell could be changed to an of the CrTe base 1 guideline materials (sand, dirt, etc).
A Wishing Stone – this small egg shaped stone has the power to conjure a large mass of clay where the user desires, by being tapped five times on a hard surface.
Flood of Clay
Creo Terram 5, R: Voice, D: Diameter, T: Individual
This spell floods the area with clay, creating 100 cubic paces.
(Base 1, +2 Voice, +1 Diameter, +1 size)
This spells are part of the free new spells compendium for Ars Magica.