So, the subject came up today, about the notion of Bloodlines for sorcerors. Someone was comparing the Draconic bloodline to the Elemental bloodline, and trying to choose between them. I was no help at all in deciding things, but I got to thinking about how elemental bloodlines might present themselves, not just in the sorceror but in his parents or his offspring.
(If you have no idea what I'm referring to, see the Pathfinder Core RPG book as well as the Advanced Players' Guide for the details. I'll wait, go on.)
Here's what I thought of.
Generally speaking, you get an elemental bloodline the same way you do any other bloodline: someone, sometime in the family tree, got it on with an outsider. How this works can boggle the mind, but for my own sanity I tend to assume that love springs or coercion spells were involved, and both parties prefer not to think about it too much. Well, at least the mortal half of the equation doesn't think about it.
There are of course the four classic elements: air, fire, earth, and water. The way I think of elements, Fire and Water never touch or mingle (or very rarely) and are inimical to each other; likewise for Air and Earth. It's actually, in my opinion, more likely that a mortal and an air elemental will mate, than two elementals of inimical elements.
The elements are not unaffected by the other planes; the celestial planes "leak" into the elemental planes, creating certain very rare elementals which bear minor celestial traits, without ever attaining the celestial template. Likewise for the infernal planes. The negative and positive energy planes also affect the elemental planes, but in those cases, I tend to think of "para-elementals" which blend other "states of matter."
When discussing bloodlines, and the traits that present because of them, I would probably rule that a character has a "main" bloodline, and perhaps a touch of another bloodline, which presents minor, non-game-mechanic traits. Elemental bloodlines can be signified by various odd coloration in the eyes, skin and hair of the offspring. Such changes persist for six generations before being "bred out."
Air colors include: blue, silver, white, purple, and any mixture thereof.
Fire colors include: red, orange, cinnamon-brown, and any mixture thereof.
Earth colors include: honey, dark browns, ochre, gray, and any mixture.
Water colors include: green, dark blue, black, pearl, and any mixture.
Touch of celestia - minor only - indicated by gold coloration of eyes or hair; rarely, accompanied by a body scent of flowers.
Touch of infernus - minor only - indicated by ash-gray coloration in skin, eyes, or hair; also sometimes indicated by a body scent smelling of sulfur.
Touch of entropy - minor only - usually indicated by a general "coolness" of already present colors and tones; the skin is cold and pale; the character displays an unusual, chilling stillness when not active.
Touch of energy - minor only - usually indicated by hyperactive behaviors; coloration is more vibrant.
Merging Elements
Where elemental planes touch or leak into each other, admixture of elements can occur.
Fire + Air = Firestorm
Fire + Earth = Magma
Earth + Air = Sand
Earth + Water = Ooze
Water + Fire = Steam
Air + Water = Mist
Energy and Entropy
Where the energy planes coincide with elemental planes, unusual elemental states are displayed.
Air + Negative= Void [super-chilled air, which can freeze objects in an instant]
Water + Negative = Ice
Fire + Negative = Ash
Earth + Negative = Stone
Air + Positive = Gale [extremely fast moving winds]
Water + Positive = Murk [water dense with plankton and other life forms]
Fire + Positive = Sun [plasma-level heated matter]
Earth + Positive = Unknown
Yeah, so that's my thoughts. For heaven's sake feel free to debate with me. This one's an idea not yet solidified into "rules."