Those touched by the influence of the elemental planes of Fire, Earth, Air, and Water are rare, but known to the prime material worlds as the genasi. Very few know, however, that there are other elemental planes that rest between those four and also between those four and the positive and negative energy planes. These are the para-elemental and quasi-elemental planes and very rarely, there are genasi who have been shaped by their primordial energy.
Unlike the typical genasi, para-elemental and quasi-elemental genasi are not usually the result of mingling between planar entities like genies and mortal races of the Prime Material. The natives of the para-elemental and quasi-elemental planes are often far too alien for that. Instead, a para-elemental or quasi-elemental genasi is usually the result of mortal races coming into contact with extreme elemental forces that can transform their bodies and souls so profoundly that the effects can even manifest in later generations.
Your genasi character has certain characteristics in common with all other genasi.
Ability Score Increase. Your Constitution score increases by 2.
Age. Genasi mature at about the same rate as humans and reach adulthood in their late teens. They live somewhat longer than humans do, up to 120 years.
Alignment. Independent and self-reliant, genasi tend toward a neutral alignment.
Size. Genasi are as varied as their mortal parents but are generally built like humans, standing anywhere from 5 feet to over 6 feet tall. Your size is Medium.
Speed. Your base walking speed is 30 feet.
Languages. You can speak, read, and write Common and Primordial. Primordial is a guttural language, filled with harsh syllables and hard consonants.
Subraces. In addition to the four major subraces of genasi detailed in other, official sources, there are the para-elemental genasi of Ice, Magma, Ooze and Smoke and the quasi-elemental genasi of Lightning, Mineral, Radiance, Steam, Ash, Dust, Salt, and Vacuum.
Where the Elemental Plane of Earth touches the pole of the Positive Energy Plane, the dirt and stone gives way to expanses and caverns of crystals and gemstones infused with the power of creation. Mystics and arcanists prize these crystals for their ability to focus psionic power or to provide life to inanimate constructs, but prolonged exposure to this plane can have radical effects on the mortal body. Those who are not killed outright as their bodies fail to cope with the influx of energy are transformed into something else. They become crystalline plane-touched and can even pass down this nature to future generations in the form of crystal genasi.
A crystal genasi's body is made of a flexible, organic, crystalline material that can move like a typical mortal form but is otherwise very alien. Crystal genasi features tend to be colorful and vivid. Their eyes twinkle in the light and their hair is vaguely translucent. Their skin is opaque and is usually either very pale and opalescent or dark and shimmering, but just below the surface of this skin, their bodies are composed of a luminous gemstone-like material.
Crystal genasi are alien, but curious. Their penchant for not quite understanding most beings and their desire to study them and learn might be mistaken as aloof or cold, if crystal genasi were not also generally very positive and friendly. Instead, they typically come off as genuine, curious, and perhaps a bit clueless about how the people of the multiverse behave. Crystal genasi who go into adventuring often do so to learn more about people outside their plane and they tend towards paths that possess arcane magic or psionic talent.
Ability Score Increase. Your Charisma score increases by 1.
Alien Mind. Because your mind is so strange and compartmentalized, you have resistance to psychic damage.
Shiny. Infused as they are with positive energy, crystal genasi can channel that energy through their crystalline bodies and focus it into a blinding shimmer. They may cast the light cantrip at will, but the range is Self, as they are only able to cause their own crystalline bodies to sparkle and shimmer. At 3rd level, they may cast the blindness spell at 2nd-level without any need for components or a spell slot. Charisma is your spellcasting ability for this spell. Once a crystal genasi casts blindness with this ability, they may not use it again until they complete a long rest.
Crystalline Body. Though crystal genasi do bleed (a colorful, shimmering blood), they are capable of sealing off parts of their bodies and even removing them without grievously wounding the whole. As a reaction when struck by a critical hit, you may negate the critical damage, turning it into a normal hit. Once you use this feature, you may not use it again until completing a long rest. Additionally, as an action, a crystal genasi can detach pieces of their body without causing themselves damage. The exact benefit or detriment of doing so is left to the DM's discretion; removing a hand might make it easy to escape being bound, but also impossible to wield a two-handed weapon. Assuming the crystal genasi does not lose their separated body part, they may reattach it during a short rest. If a crystal genasi does lose a detached body part, they may only replace it by obtaining crystal from the Quasi-Elemental Plane of Mineral. If they somehow lose more than half of their body this way, a crystal genasi immediately goes to 0 hit points but is stabilized and unconscious until brought in contact with the positive energy-infused crystals of their native plane.
Between the Elemental Planes of Earth and Water lies a vast expanse of sludge and muck. Closer to the Plane of Earth, the mire is a thick and threatens to entomb anyone who travels through it. As the expanse nears the Plane of Water, it thins out to a slimy, acidic sea. Most mortals exposed to the primordial forces of Ooze do not survive to tell the tale, leaving only preserved remains buried in the muck. But those who do are often changed, leading to the creation of ooze genasi.
The appearance of an ooze genasi can vary, but all have a slimy outer "skin" and soft, malleable bodies. Some have skin tones of rich, deep brown, while others shimmer in almost-translucent blues and greens. Often, their eyes are the same color or similar to their skin tone and their "hair"--if they have it--is merely an extension of their slime-coated bodies.
Ooze genasi are expressive beings, both proud of their self-reliance and bitter at their lot in life. Whether they are broody or dramatic, an ooze genasi wears their heart on their sleeve. Those that end up in an adventuring life tend to fall in with a bad crowd, using their natural talents as thieves, pirates or other "scum."
Ability Score Increase. Your Dexterity score increases by 1.
Acid Resistance. You have resistance to acid damage.
Amphibious. You can breathe air and water. Additionally, you can breathe even in murky sludge-filled environments.
Slippery. Your coating of slime makes you remarkably hard to pin down. You have advantage on any check to escape grapple or restrained conditions. You also have advantage on any check to escape any physical bonds.
Semi-Amorphous. Your skin, musculature, and skeleton are all much more flexible than those of a typical humanoid. You may squeeze into any space large enough for a creature two size categories smaller than yourself and you suffer no penalties squeezing into a space large enough for a creature one size smaller than your own (see Squeezing into a Small Space on page 192 of the Players Handbook). This ability does not extend to your possessions and gear; those must be able to fit through the smaller space on their own or be left behind.