Half-Mariel individuals are rare and only occur during the five year period when their Mariel parent is on land. Outside of this period, Mariel are genetically incompatible with other races. Mariel undergo epigenetic changes around the age of twenty-five to transform into a terranean biped and then again five years later to return to the sea. This transformation is a means for Mariel to interact with the terranean races but romances and especially producing children, is highly discouraged during this time for the complications that come with it.
Though thoroughly warned of the consequences of these inevitably brief affairs, some Mariel do have flings or fall in love with individuals of other races in their time on land. These relationships can end in heartbreak when the Mariel approach thirty and are compelled to return to the sea once their transformation back begins. If they do not return, they are trapped as bipeds for the rest of their lives and stripped of their Water Elementalism.
Half-Mariel are born as bipeds and have a reversed transformation cycle from their Mariel parent--but this occurs at the same age for a half-Mariel as a full-blooded Mariel. For Mariel who have birthed or sired a child on land, this means that they are torn between abandoning their children or abandoning their people, identity, and god. If a female Mariel is pregnant during her transformation period, the physical stresses of the transformation can cause miscarriage or pre-term delivery. A Mariel would have to wait until their interracial child was an adult to potentially see them again if they return to the ocean.
Half-Mariel have no distinct traits that identify their aquatic heritage in their early life. They inherit the long, tapered ears of the elemental races, though half the length, from their Mariel parent. They can potentially inherit brilliant, unnatural hair and eye colors from their Mariel side.
If they transform, their Mariel features will generally match their Mariel parent--such as scale colors and patterns, and fin shape. Half-Mariel who remain on land may always be marked with more obvious Mariel traits. This can include the emergence of scales on prominent regions such as the hips, thighs, shins, elbows, knees, collar bone, jawline, cheekbones, or brow; webbed fins between the fingers and toes; gills on their flanks which can be partially functional or superficial; or an emergence of small fins along the back of the forearm or sides of the legs.
At the age of twenty-five, half-Mariel feel compelled to seek and enter the ocean. However, the half-Mariel transformation is not as absolute and unavoidable as it was for their Mariel parent. Some half-Mariel may experience the appearance of certain aquatic traits, such as scaling, webbing between the digits, the beginning of gills, and pains in the legs. Others may not experience any obvious physical changes until they reach the sea.
The transformation can be avoided. If a half-Mariel never reaches the sea, after about twelve to sixteen months from the onset of symptoms, the urge will stop and they will remain bipedal, but any traits that emerged in preparation for the transformation will remain.
If a half-Mariel undergoes the transformation, they also have a five-year period during which they will live as Mariel. At the end of those five years, they can potentially return to land or choose to remain and live as a Mariel. Around the age of thirty, they will feel urges to return to land and experience mild physical symptoms that hint at the potential of transformation, but all of this is less pressing than their previous transformation symptoms. If they choose to remain, their body will remain aquatic after. If they choose to return, the transformation back to a bipedal form, they will lose all physical Mariel traits when they change back.
Individuals of one-quarter Mariel blood may undergo partial transformations but they cannot fully transform. They too feel a draw to the ocean, but not as strongly as their half-blooded parent. The partial transformation may be initiated if they come in contact with seawater around their twenty-fifth year, which leads to the emergence of traits previously described in half-Mariel's pre-transformation phase. These traits will remain life-long and there is no secondary transformation phase five years later. One-eighth Mariel may have some minor scaling appear around twenty-five but no other traits. After this generation, no further Mariel traits appear.
A descendent of a half-Mariel that remained in the ocean and bore children with a full-blooded Mariel is generally indistinguishable from pure blooded Mariel aside from any phenotypical traits from their non-Mariel ancestor.
Born to a Mariel mother, a half-Mariel would have an ability for Water elementalism. Born to a mother of any other elemental race, the offspring would gain her ability. Children of a Mariel father gain no elementalism, which is an added complication for half-Mariel when they feel the urge to return to the ocean. While they can survive without magic, they are handicapped in comparison to Mariel. Without elementalism, these individuals generally deny their transformation or return to land after five years.
As Mariel live for around three hundred years, a half-Mariel with a human parent would live for around one hundred and fifty years. With a parent of a longer lived race, their lifespan would be a median between the two parents’ races.
Like the other elemental races, Mariel have a suspended aging process that begins at the age of twenty-five (the same age as their transformation) and continues until the final decades of their life. Half-Mariel have this same aging process.