Acid "fire" shield

[Allegro]

I’m curious what energy a fire shield spell cast with an energy substitution of acid or electricity would protect from. Would an acid “fire” shield protect against electricity and vice versa?

 

[Sejs]

By the rules, just casting the spell with the Energy Substitution feat would not change the element that it protects against, just the element it deals damage with.

Thematically, if you had an 'acid shield' spell, it would protect against electricity (and vice versa). Acid is earth-associated, electricity is air-associated.

 

[Cheiromancer]

How about a sonic variant? Would it also protect against sonic attacks, or would it be paired with force?

 

[Aust Diamondew]

I don't think sonic and force have ever been paired in any material I've seen. Neither represent any of the four elements, which all can be easily paired off.
I've probably just have a sonic shield counter sonic and a force shield counter force unless someone had a better idea.

 

[Sejs]

How about a sonic variant? Would it also protect against sonic attacks, or would it be paired with force?

Sonic doesn't have an elemental association, so it doesn't have an opposite. I've always thought sonic made logical sense as air-associated, but I can see why they didn't. Likewise force - no association, no opposite.

So with that in mind, for the sake of simplicity I'd say that yeah a sonic shield would deal sonic and protect against sonic, as would a force shield deal and protect against force.

 

[Cheiromancer]

I once toyed with a scheme in which each element was assigned two energy types: fire gets fire (duh!) and electricity (bright forms of energy); water gets cold (ice) and acid (usually a liquid), air gets force and sonic. Earth gets positive and negative energy. This system would support a cold/fire and acid/electricity opposition based on the fire/water opposition. The two energies of fire cancel the two energies of water.

Unfortunately earth (associated both with life and death) would have to be its own opposition. And so either force and sonic cancel each other (which kinda makes sense; force is air forced to be rigid and stiff, sonic is air set to vibrating intensely), or they cancel themselves. I can't remember if I ever made a decision.