Background: Sirens are mermaids with wings, capable of flight, and can take the form of beautiful women. Besides their natural charisma and allure, Sirens have the following traits:
Enchanting singing voices that allow them to influence people's emotions; they prefer to use issue commands in song form. Their vocal cords can take the strain of singing over and over without weakening, a Siren still has to breathe but they can go without for thirty minutes of nonstop singing. However, after that, they really need to take a breather (literally) of five minutes at the most.
The grace of a dancer and a charisma-fueled aura. That combination (graceful movements and charismatic beauty) makes them literally hypnotizing.
Natural (and magically enhanced) gift of intuition; Sirens can "read" people, and are really, really good at understanding and manipulating them.
Hydromancy-Sirens are creatures of the sea, and can condense and manipulate water (think the Waterbenders in The Last Avatar). Additionally, they somehow have the power to heal wounds in those around them (only within a six-foot radius); mages theorize the purity of their singing or their connection to the life-giving sea, perhaps both, makes this possible. A Siren can heal seemingly fatal wounds, even restore limbs, but they can't heal things like a mace to the head or being cut in half.
So, in medieval warfare, what impact would Sirens have?
- Morale-Music is powerful, magical music is more powerful, but if a Siren is singing a jubilant tune after the general's been cut down, you better believe it won't do a darn thing. There's only so far magic can go.
- Hydromancy-A Siren's capacity to cause rain, fog, or liquidation (in small areas) can be life-saving, even gamechanging. However, I'm not sure how powerful it will be. Sirens can only affect a small area at one time, so they can't, say, cause a tsunami or a flood.
- The combatants are the English and the French; we have Beren (this world's version of Napoleon) and Wallace (this world's version of William Slim). Both armies have 10,000 troops on the battlefield, which is mostly plains with some hills (think Kansan prairies). The British have sirens, the French do not.
- I'm certain Sirens can help with morale, medicine, recruiting, and so forth. What I'm wondering is if I have missed anything else that I might need to put in.