So, to further expand on the Planes and their inhabitants, I bring you the Quasi-Elemental Genasi.
Quasi-Elemental Planes exist where the Elemental Planes meet the Positive and Negative Energy Planes (go check out the map in the last post). These are the Light and Dark sides of the relatively Neutral Elements - let's start with the Positives (mainly because the Negatives are far more interesting).
The Radiance Genasi are what happens when Fire gets Positively charged - bright, happy, shiny people. Their Plane is a place of colour and beauty, and they tend to find the Multiverse... a little underwhelming. Many take to the arts in an attempt to bring some of the brilliance of their home to the rest of the Planes - but when you are used to unlimited shades and colours that don't even exist outside of Radiance, it's kinda hard. Being very positive in their outlook, few are deterred by this.
Mineral is Positive/Earth - The Earth takes on qualities of beauty and radiance, becoming precious gemstones. The Mineral Genasi are kind, generous people, who just so happen to be huge, walking collections of gemstones and crystals. Pretty cool NPCs, especially as traders, salesmen and maybe hireable miners or appraisers (who would know gemstones better than a gemstone?). They are also known for their generous nature - when you live amongst gemstones, they lose some of their value, and money holds little appeal to them. You might see one working in a free clinic, healing the less fortunate, or otherwise helping the needy.
Steam are described as "The Lanterns in The Mists" - and are a race determined to get to the bottom of things. Skilled in deductive reasoning and grunt work, they make for perfect private eyes. I feel that this is too focused for a race - a single character, fine, but a whole race of detectives? Meh.
Lightning Genasi come from a Plane of storms, static and energy. When Air gets supercharged with energy, it starts sparking - and Lightning comes with it. For a cool twist, Lightning Genasi are obsessed with a particular facet of the Multiverse - Gods and Powers. The reasoning being, well, your Gods of Water love to go for a swim, Gods of Fire enjoy an inferno, but Powers of Thunder, Storms, and Lightning tend to really revel in the joys of a good storm - so why not go visit The Storm? Many Lightning Genasi have encountered a Power on the Plane, and they find them fascinating. Many who then go on to become Planewalkers will then spend their time investigating other religions, mythologies, and Powers to see what they do. Many even simply travel from temple to temple, learning as much as they can about Gods of all stripes. Make good Clerics, obviously, but I can also see a cool "Religious polymath" - one who knows a million and one little prayers or holy symbols to help out in a specific situation. Picture the party being faced with some very specific Undead: the Gensasi holding up holy symbol after holy symbol, reciting words of Power, hymns and litanies, until finding just the right one to dispatch the terror. Very cool.
Next, The Negative Quasi-Elemental Genasi. Confused yet? I am.