Ignatius of Flambeaux was an Elementalist magus who fought against the Sahir in Iberia. Due to a terrible Twilight experience, he found himself able to convert his own life essence into Aquam vis, which the aggressive Flambeaux helped fuel his personal battles by rarifying water elementals out of the ocean. After gaining the allegience of a number of them, he developed an array of spells to transform them into other elemental types for his use.
(Design note: Totally up to your saga if this actually works. Or how it works. Does it change a water elemental into a fire elemental? Or a Water Elemental whose body is on fire, but maintains the water elemental powers?)
The Tidal Shift of Elemental Alignment (Muto Aquam[FORM] 35)
R: Voice, D: Diameter, T: Individual
This spell transforms a rarefied water elemental into another Form of elemental, and extra care was taken during the design of this spell to allow the elemental to flow naturally into a new Form: Earth, Air, or Fire. It must penetrate the elemental's magic resistance to have effect. The spell requires a casting requisite of the new Form. It can effect an elemental up to size +4. Due to Ignatius's casting sigil, the elemental being transformed creates a sound like mad laughter that fades as the spell continues.
(Base 10, +2 Voice, +1 Diameter, +1 to decide which Form on casting, +1 size)
Side Effects table (1d10)
1 Exaggerated Sigil: The elemental's body is twisted into a form where it appears to have monstrous human-like features twisted in a rictus grin, and the sound of laughter follows it everywhere.
2-3 Minor Flaw: Despite its change of form, the former water elemental thinks of itself as a water elemental. It may seek out bodies of water to plunge itself into, and not react how an elemental of its new form should act, like a fire elemental not realizing that its body will burn people it touches, rather than getting them wet.
4-5 Minor Side Effect: Transforming the water elemental into a new Form, the noises made by its movements, actions, and powers still sound like crashing waves.
6 Minor Benefit: The elemental maintains its affinity with its previous element, as well as its new; Elementals of both forms will consider the new elemental one of its own.
7 Major Flaw: The transformation into a new form is uncomfortable, and the elemental will feel a great rage towards the caster - Rego control magic may be recommended.
8 Major Side Effect: As all elements are mutable, when the elemental is transformed, a counter-elemental reaction will also follow it around. Fire elementals will chill the ground beneath them while still burning things nearby; Earth elementals will weaken and disrupt earth they pass by, as if they were a giant plow; Air elementals will leave a strange, stale air in their wake, as if in a locked tomb.
9 Major Benefit: Should the elemental be damaged while it is transformed, the vis that is left behind can be used as either form.
10 Fatal Flaw: The transformation of the elemental into a new Form causes incredible damage, as the magic does not change it all at once. The water elemental's body boils away, gets dispersed as a wet mist, or rudely is displaced by sudden surging rocks in its depth. Casting the spell immediately causes the elemental to lose 10 might, scattering the bits of itself everywhere and likely destroying the vis those parts of its body held.