I was wondering about something, and while it may seem like a logical thing to me, I'll ask for everyone's opinion on the matter of combining different schools of arcane.
Would a mage, or someone who can channel different schools of arcane magic, be able to combine, and/or alter an already existing spell, to create something with a different effect.
Think of Frostfire, Shadowflame, Shadowfrost, or Spellstorm, for example. They are a combination of two elements, but are they depend purely on one school of magic?
There is a frostfire bolt I believe that a mage can learn should they go the flame talent stream. In fact, here's the
link
Well, I think Blizzard had to put it -somewhere-. It doesn't necessarily answer the question whether it is a combination of fire and frost, or purely a fire spell. "Shadowflame" spell is in Destruction tree for warlocks, but Destruction warlocks use fire, and shadow spells too.
Don't forget things like Frost Ward, and the likes. Lots of spells are abjuration, flavored with other elements. In terms of RP on CotH, I wouldn't mind it, if it were an X-oriented mage uses their forte to cast spells of a less familiar school, with it having strengths and weaknesses relating to the caster's primary school.
If you're just combining things for show, like a firey frost bolt, I wouldn't mind it, as long as it would be balanced to a point that the combination freezing-burning effects of your spell wouldn't be any more "powerful" than a single-element burst of ice or fire from an equivalent mage.
As for the effects... Getting shot with a bolt of ice damages one differently than a fireball, right? If you wanted to combine, say, lightning and cold for a sensory-overloading nerve damage effect, creativity is cool, as long as it doesn't go too far into the impractically silly and contrived.
I generally regard "crossover" spells as more of a case of an individual caster imposing his or her will upon the element in question. Frostfire Bolt is, arguably, a bolt of Ice that the caster just so happens wants to be on fire, and is skilled enough in the Arcane in order to be able to impose his demand on said element.
In terms of Divine Spells, my character, Sariella Tanu'Belore, possesses a high amount of skill with regard to Holy Magics (she's a Blood Knight, offensive-spellcasting specialty), and is able to impose her will upon the Light in order to make it behave more like fire (IE; Holy Fire, an existing spell), Holy Shock (I imagine this is the caster imposing their will to create a holy bolt of lightning), and a spell of her own creation, Holy-Chain-Lightning, which seriously needs a better name, but bleh.
Realise, however, that your spell probably isn't as effective if you want it to behave solely like the element you're representing. Sari's Holy Fire, whilst it can't be extinguished like regular fire, doesn't burn very rapidly at all and pretty much functions more like a sudden heatwave with a negligable DoT than would provide any real burning effect, like a real pillar of flame might. Her Holy Shock (and Holy Chain Lightning), whilst striking forth like a bolt of lightning, isn't enhanced by things like metal, grounding, and doesn't interfere with the targets nervous system. They do however carry forth a portion of what a Holy spell would typically do.
So whilst a Shadowflame spell might "burn", it won't do so as well as a simple Flame spell.
I vouch for Dae's explanation here. Seems the most logical. Blame Blizzard for their half-written lore. :/