The original Goliath clade was created to meet the need for strongmen, bouncers and the like for the many shady businesses that had sprung up in the Jovian system. However, as big as they were their design was still a compromise, they needed to be large and strong enough to intimidate their victims but small enough to move easily through habitats that were often built for smaller clades. When it became possible for Goliaths to live in habitats built to their own needs some took the opportunity to overcome these restrictions. In one group a compelling meme took hold: 'The "smalls" had made them different by making them big so they would make that difference their own by making themselves bigger.' The long process of making themselves bigger began with straightforward selective breeding pressure. In this group bigness became a measure of attractiveness and parents soon turned to gengineering to give their young the competitive edge in finding mates. The question almost every parent asked the gengineer was "how big can you make them?"
From the fossil record of Old Earth they knew that the largest animals ever to walk the land in standard gravity were the sauropods and that the brachiosaurids were the tallest with some, like Sauroposeidon, possibly reaching up to 18 metres high (lazurogenics would later confirm this). However this alone did not answer their question as to 'how big could a biont with a hominid bauplan get?' because the sauropods weren't bipeds. Still it was a goal to aim for and evolution had already found many tricks for increased sizing that they could learn from. And so began the Nephilim.
Breaking their connections to organized crime was the first step. That lifestyle was a violent one and the Goliaths were created to take and 'dish out' a lot of physical abuse. Their muscles and bones had to be excessively large, even for their great size. The Nephilim, on the other hand, could lead a more civilized lifestyle and would only need enough bone and muscle mass to be active in their environment. For them "bigness" may be a measure of attractiveness but at the same time being too muscular is seen as a throwback to the past, so for the Nephilim the question of 'how big?' really became a question of 'how tall?' Compared to the Goliaths the Nephilim are gracile (or at least 'not muscle-bound'), they are tall and thin with their upper bodies tapering to the top, an effect that only enhances the impression of great height when one stands at their feet and looks up.
Great size puts a lot of strain on the hominid bauplan so the Nephilim have made every effort at lightweighting their form to gain height. Like birds the Nephilim have smaller, more efficient organs and a system of air sacs reaching out from their lungs to fill out the volume of their bodies. This network of air passageways reaches even to inside most of their bones and out to their skin; whereas humans have a layer of fat to insulate them and store metabolic calories, the Nephilim have spongy layers of cells under their skin and around their organs that store light hydrocarbon gases. A by-product of their digestion, these gases (mostly methane) are filtered out of their guts, cleaned and passed through a branch of the air sac network to their spongy layers. Once there, colonies of neogen bacteria consume the gases and pass on the ATP they make into the Nephilim's bloodstream. Even with the Nephilim's large size dwell time for the gases is less than a week, but that is more than enough to hold them over between meals.
This system of air passageways and spongy layers has allowed a further reduction in weight by way of blood volume. Because Nephilim blood can now be resupplied with oxygen and energy carriers locally their blood flow can be reduced to most organs. There is a trade-off in this however as the other constitutes of the blood (carbohydrates, proteins, salts, etc.) are also reduced. As a result the Neplilim have much slower growth rates and less natural ability to heal from injury.
To help fight the effects of inertia most of the muscle mass that moves their limbs is repositioned so it doesn't move so much with their limbs, while some of that which remains is now rededicated to actively pumping blood back up from the lower levels. Even with this "repositioning" their limbs still look thick and bulky due to the greater diameter of their hollow bones. The Nephilim skeleton also has some other basic changes to the hominid bauplan, a head to toe reorientation towards gaining greater height and bearing the mass that comes with it. For example, the Nephilim's foot is squarish (as wide as it is long) with an enlarged little toe to give it a thrusting toe on each side. In Nephilim's legs, which are extra long for more height, the tibia and fibula have been fused into a single bone. Both this lower bone and the femur are large diameter, yet hollow, load-bearing tubes. And while their walls are thicker than most other bones in the Nephilim's skeleton they gain most of their strength from being heavily fluted.
Another change is in their pelvis. As an evolved structure the baseline human pelvis is really a quadruped's pelvis readapted to bipedalism. The Nephilim felt they could do better with a simpler structure. They didn't see a need for as much range of movement in their legs (they weren't planning on being acrobats and running would be too stressful) so they were able to place the pelvic acetabulums lower with more of a downward face that can better transfer loads to the ground during the long strides of Nephilim walking. Of course such a placement would have made intercourse and childbirth more difficult had they not also chosen to relocate their reproductive systems to be above their reshaped and lowered pubic bones.
Their backbones are also simpler. A baseline human backbone has 26 vertebrae and four curves that give it an S-shape. The S-shape allows the backbone to function as a spring rather than a flexible rod, thereby absorbing shock during walking and running, enhancing the strength and flexibility of the backbone, and facilitating balance when upright by placing the trunk directly over the feet. A Nephilim backbone only has fewer but longer vertebrae and doesn't curve nearly as much, but as the Nephilim can't run and are in fact known for moving with slow, deliberate care (because a fall, with their great height, carries an even greater risk of injury) they avoid most jarring movements. Heavily padded feet and thick disks in their longer necks are enough to absorb those shocks that remain.
Those last two changes (in the pelvis and backbone), and their great height, make lying down to sleep a real challenge, to say nothing about getting back up. Fortunately the Nephilim gave themselves an augmented sense of balance and can now sleep quite well in a vertical position. They simply need to lean against some support, such as a large tree and although their sense of balance functions even when unconscious they typically take the precaution of anchoring themselves when they go to sleep.
Their augmented sense of balance isn't their only improved sense. The Nephilim have many visual augments to improve sight. Like Goliaths, they have extra visual cells in their eyes for some improvement in their night vision, but it is the larger heads of the Nephilim, which allow for larger eyes capable of gathering more light, which gives them the real improvement of night vision. A larger eye, with a larger fovea, also has an intrinsic ability to see better at greater distances. [A fovea is a small region of the retina where the concentration of rods and cones is the highest and therefore vision is the sharpest.] The Nephilim have also enhanced this by again taking a clue from birds, they now have a bird-like pecten structure in each eye. [A pecten is a thin, greatly folded structure of capillary rich tissue extending from the retina to the lens.] The pecten supplies nutrients and oxygen throughout the vitreous humour of the eye, thereby reducing the number of blood vessels needed in the retina. With fewer blood vessels to scatter light coming into the eye the Nephilim can have even sharper vision. Also, normally the vitreous humour in a hominid eye is a jelly but in the Nephilim eye the vitreous humour is a true fluid. This not only allows the nutrients and oxygen to be quickly circulated within the eye but also allows the vitreous humour to be passed through filter in the pecten that removes any cellular debris floating in it, thus maintaining its ocular transparency. As another feature, the Nephilim eye actually has two lenses, these work together with the cornea as a 'triplet lens system' to overcome any Seidel aberrations. Correcting these aberrations has an additional effect of allowing the Nephilim eye to benefit from an even larger aperture (which means even better angular resolution) so the Nephilim have also given themselves cat-like irises that allows the pupils to open very wide when light levels permit.
Like the Goliaths, the Nephilim also have an extra opposable thumb on each hand and a disproportionately large nose for a more acute sense of smell.
While the Nephilim definitely have the largest heads of any humanoid clade, their heads (and brains) are not proportional to their size. The aforementioned 'tapering effect' has given them a skull that has only 50% the volume it would have had for a direct scaling up while the needs of "lightweighting" further limited the size of their brains. Still Nephilim grey matter does have enough mass for a First Singularity intellect (but only just enough and only if optimized for such) and ascensions are not unknown in this clade, however those that do become transapient also tend to become post-Nephilim as their interests expand beyond the Nephilim's somewhat narrow focus on increasing their height. The average toposophic level for a Nephilim is therefore only superbright but they do have a high incidence of transavants.
By necessity, the Nephilim are non-violent and avoid personal conflict. The reason is simple, a fight could mean a fall and with their great height a fall carries an even greater risk of injury than a punch or kick. For the same reason they are adverse to physical risk-taking in general and do not reward or praise members who engage in risky activities like competitive athletics.
However, the Nephilim do enjoy wide open spaces and even seem to share a form of collective claustrophobia. They live exclusively on terraformed worlds and larger open air mega structures[1,2,3], spending most of their time 'outside' in a tech-nomadic lifestyle, which is a very scaled down version of the "Vagabond Way" found on Kiyoshi. Preferring to walk, the Nephilim have to travel light so they typically carry on their person the most flexible and multipurpose tech they can get to meet their daily needs. For example, almost every Nephilim carries handtech that allows them to handle things at the smaller scales. Some Nephilim, like those who wish to live-off-the-land, even go so far as to have a swarm of such units to collect food for them.
The Nephilim mostly travel alone, often with a pet (Nephilim pets are giant megafauna in their own rights, with very large lazurogened prehistoric animals currently being the most popular) or in small family groups, but they are not isolationists or anti-social. The tech-nomadic lifestyle allows them to remain remotely connected to the greater society at all times. In fact, this 'connection' is vital for the transavants as it gives them access to jobs that occupy most of their savant mental capacity and helps them fight off the psychological problems that sometimes come with transavanthood. Furthermore, this connection has allowed some of the transavants to become members of tribeminds, which in turn has helped to keep the Nephilim culture competitive.
Even though the Nephilim are one of the 5 distinct subspecies of Goliaths they have always been relatively few in number as they are a specialist species. The range of the Nephilim is also limited because they don't travel well in ships or other vehicles. (Nephilim saying; "A true nomad walks.") They find even the largest ships to be too confining and will only travel this way if they can do so in stasis. When they do travel in ships it is to find new places to settle - for the Nephilim the tech-nomadic lifestyle means 'settling a world but being a nomad in it.' Although you might find a small tribe of Nephilim settled in any of the sephirotic empires, most have preferred to live in the Mutual Progress Association, where there is an over-abundance of megastructures to roam. You can also find many Nephilim in the Utopia Sphere, which has large numbers of MPA megastructures on long-term leases, and the Zoeific Biopolity, which has not only built and/or terraformed large numbers of planets but also has more than its fair share of MPA megastructures on long-term leases.