Planetouched
Planetouched is a general category of races that shows up in Dungeons & Dragons and Pathfinder. Semi-official, it is a general term for races who have mortal ancestors, but who are marked by the outer planes.
In other words, someone whose ancestor heroically refused to allow dimensional barriers to stand in the way of humanity's endless quest to put their penises inside of non-humans. Or, conversely, a woman brave enough to face the dangers of angel/demon/elemental cock. Generally, the first-generation products of these sorts of things are a bit too powerful to fall into PC hands, so most of the races below are the result of watering around that extra-planar potency a bit through a few generations of interbreeding with mere mortals.
Sure, theoretically it can also manifest as a result of arcane pacts, exposure to planar energies in-utero, wizardly meddling, blessings/curses (particularly by planar beings) and all other sorts of non-sexual stuff. But, as with sorcerer bloodlines, everyone's imagination immediately jumps straight to the porn.
Planetouched have always been popular choices for PCs since their introduction. There's the Mary Sue factor, sure, but there's honestly plenty of potential there for interesting concepts. And, as the editions go on and more and more people recognize Level Adjustment as the swollen inoperable cancer it was, playing one has only gotten easier and more-attractive.
Tieflings
The original and, in the eyes of many, the best Planetouched, tieflings started it all when they appeared way back in the Planescape Campaign setting. They are the descendants of mortals and fiends - the denizens of the Lower Planes.
The general tiefling is expected to be of human ancestry; demihuman tieflings consist of the Fey'ri (Elf) and Tannaruk (Orc) from Monsters of Faerun, the Maeluth (dwarf/devil) and whispling (halfling/demon) in the Fiend Folio, and the Worghest (goblin/barghest) from Dragon Magazine #350. Pathfinder actually stated out a number of different strains, originating from mortals with one predominant kind of fiendish ancestor.
For more details, see their page: Tiefling.
Aasimar
The opposite-aligned counterpart to tieflings, aasimar trace their lineage to the Upper Planes and its resident celestials.
There are far fewer aasimar/demihuman crosses, with the only named example being the Celadrin (elf/eladrin) of Dragon Magazine #350. However, Pathfinder still gave them a lot of varieties from different kinds of celestial ancestor.
For more details, see their page: Aasimar.
Genasi
Seeing the pattern here yet? These are your basic Elemental Planetouched, with powers relating to earth, air, water or fire. This might be the result of actually boning a creature made of primordial fire (no mean feat!), or of boning the properly-aligned elemental genie.
For subraces, we got two demihuman-specific crosses (the Dwarf/Azer hybrids called "Azerbloods", and the Halfing/Genie hybrids called "D'hin'ni", both from Dragon Magazine #350), and an assortment of alternate elemental affinities. Dragon Magazine #297 gives us Paraelemental Genasi (Dust, Ice, Magma, Ooze, Smoke and Steam), 4th edition made lightning & thunder-themed "Storm" Genasi part of the defaults and had Athasian Genasi of Sand, Ember, Sun and Magma and corrupted "Abyssal" Genasi of Caustic, Plague, Cinder and Void, whilst a Ravenloft fan-splat called Quoth the Raven #7 has Dread Genasi (Grave, Mist, Blood and Pyre).
Yet again, check their page out here: Genasi.
Pathfinder reworked the concept a lot, with four distinct races filling out the roles of "elemental Planetouched," plus the suli, who originate from jann genies and have a bit of all four elements inside them.
Axani
Hailing from Dragon Magazine #297, the axani are the inevitable "Axiomatic Planetouched", to contrast the Upper, Lower and Elemental Planetouched we already got. They're associated with all the Lawful Neutral planars, and to a lesser extent the ultra-lawful Upper and Lower Planes. They look very well-formed, always having symmetrical features, and may occasionally have a metallic tint to their skin and/or hair. They're extremely organized, disciplined and regimented, as you'd expect of someone with pure Law in their bloodline. They've also never been nearly as popular as the first three, possibly because the axiomatic outsiders are purely a construct of the RPG writers with little basis in real-world mythology to prick the imagination, possibly because outside of the robots Law outsiders have always been pretty damn boring.
They're Medium sized normal-speeded Native Outsiders with +2 to both Int and Wis (though their ability fluff states that they are "logical and calculating, but tend to be cold and emotionless", implying they were supposed to get a Wis or Cha penalty), Cold & Sonic Resistance 5, a spell-like ability (Calm Emotions 1/day as a Cleric of their character level), +2 racial bonus to Diplomacy and Spot, and Darkvision 60 feet. Their favored class is Monk (what did you expect?) and they get a Level Adjustment of +1, like all the other Planetouched from 3.5.
There are a number of sub-categories thereof:
- Mechantrix: No, not some sort of dominatrix warforged monstergirl, unfortunately, as awesome as that might be. (Damn it!) These are planetouched who (somehow) display heritage connecting them to the mechanical outsiders of Mechanus -- the Modrons and the Inevitables. This is usually non-sexual, for obvious reasons. Visually, mechantrixes look like their humanoid ancestors, but always have at least one clearly mechanical or inorganic physical feature - razor-blade hair, clockwork eyes, pipes sticking out of veins, etc. Their skin is usually smooth and has a metallic sheen. They originated in the Fiend Folio. Being presented in monster manual format, it's harder to make out their stats as a playable race; what's clear is that they're Medium sized Outsiders who can Shocking Grasp as if they were a Sorcerer of the same character level 1/day, they have the Electricity Healing trait (immune to Electric damage and instead heal 1 point of damage per 3 points of Electric damage taken), they get a +2 to Spot checks and a +4 to Knowledge (Architecture & Engineering) checks, their favored class is Fighter, and they have a Level Adjustment of +1.
- Zenythri: Short version? Some other lawful outsider knocked up your grandma. These originated in the Monster Manual 2, and so in the eyes of some DMs, these are the "official" Axiomatic Planetouched, so they're slightly more likely to let you play one than they are to let you play an Axani. They look like impossibly perfect-featured humans; a zenythri's skin is flawlessly smooth, and its muscles are well defined and taut. Even its hair falls effortlessly into place around its handsomely chiseled face. The only real give-away (besides the looks; no human is that good-looking) is the fact their skin and hair always has a slight blue or purple tint. Like the Mechantrix, they have a Monster Manual format, making their player character stats hard to reverse engineer. Like Mechantrixes, they are Medium sized Outsiders, with Resistance 5 to Electricity/Fire/Sonic attacks, a True Strike 1/day spell-like ability (caster level equals character level), and a +2 racial bonus to Balance and Intuit Directions. Their favored class is Monk and they have a +1 Level Adjustment.
Cansin
The axani's counterparts, the cansin are the spawn of pure chaos, serving the role of "Anarchic Planetouched," right down to never being as popular or well-supported. The purely chaotic outsiders, again, have never been the most interesting, and in fact have tended more towards "lol! Random!" Chaotic Stupid behavior and antics.
Cansin look like humans but always have some strange trait that emphasizes their anarchic nature. Some examples include eyes that randomly change color (and not in synch with each other), irregular features, and an "aura of randomness". They always seem disheveled and disorganized, no matter how hard they try. Statwise, they're Medium sized normal speed Native Outsiders with +2 Int and +2 Cha (though, again, they have fluff implying that should be a charisma penalty), Acid & Fire Resist 5, Entropic Shield (caster level = character level) 1/day as a spell-like ability, +2 to Bluff and Search checks, Darkvision 60 feet, favored class of Sorcerer and Level Adjustment +1.
- Chaond: Coming from the Monster Manual 2 in 3.5, the chaond are demonstrably tied to Slaadi rather than any generically chaotic outsider. Not usually the result of mating with a slaad, simply because slaadi "mate" by laying their eggs inside of other creatures with all the romance of a bot fly so their larvae can eat their way out. They have stocky builds, long limbs and blocky facial features, as well as colors that constantly shift at random. Like their Zenythri counterparts, they have a Monster Manual format, making their player character stats hard to reverse engineer. Chaonds are Medium sized Outsiders who have Resistance 5 against Acid, Cold and Sonic, receive a +2 bonus to Escape Artist and Tumble checks, and can cast Shatter 1/day with a caster level equal to their character level. With a Level Adjustment of +1, they treat their very first class as their Favored Class - so a Chaond who starts her career as a Fighter has Favored Class (Fighter), whilst her sister who took the path of the Warlock has Favored Class (Warlock). Sadly, this betrays a stunning ignorance of the rules, as multiclassing relies on a starting class being different from a Favored Class to avoid XP penalties.
Shyft
The ghost-like shyft, documented in the Fiend Folio, owe their lineage to the Ethereal Plane. There's not a lot else to say about them, since the Ethereal Plane has always been the most BORING of the planes, and they haven't really been updated since. Seriously, who can even name any of the outsiders native to the Ethereal, hmm?
The fact that their racial stats are set up in Monster Manual format, and absurdly overvalued, certainly doesn't encourage you to play them; at the cost of a +3 Level Adjustment, you get to be a Medium Outsider with low-light vision, Cold/Fire/Sonic Resistance 5, +4 to Hide & Move Silently, and Ethereal Jaunt 1/day (9th level or character level, whichever is higher).