Appearance

Adna

The anatomy varies, but their flesh has a somewhat leathery texture, light grey and modeled patterns that tend to act as camouflage. Honestly a colorless image of another creature would already be pretty close.

Ange

The facial/skull structure is similar to Harg. They have the human-style flat faces, since the jaw is not intended to be a weapon. The area a nose would be is basically a sheet of bone (with skin and small muscles over it, as normal), same as the rest of the non-orifice-skull. The eyes are significantly larger and the iris composes most of the visible eye (you cannot really see the white), with the standard large predator circular pupil. Up to you on the angle of the eyelids, but they can close their eyes and do blink to maintain moisture.

The jaw is larger than on Harg, but still proportionately narrow and angular in comparison to the skull (by human standards). The mouth is pretty similar in principle to humans, lips covering the teeth and containing intricate micro-muscles for expression.

Ange have bone structures on their scalp to a similar effect as hair or a headdress. It is composed of numerous plates and is not as flat to the skin as on the rest of the body (somewhat ridged). Not huge, but they definitely make it hard to crack an Ange’s skull (unless you hit the face directly).

The osseous plates cover parts of the body that do not need to flex very much, but places that need to bend are either small and separate plates or just skin. It is less like full body armor than extra protection where it will not get in the way.

As for build, they fall into the human female structure on a skeletal level. Unlike Harg, Ange do pass their offspring through the pelvic opening, to pretty much the same effect it has on human body structure. Of course, Ange do not lactate (or care for their young at all), so no breasts (the Dominion is probably going to be overlooked for harem anime adaptation).

Their limbs are a bit longer than humans, and the angles and range of their joints are off from human, but I will mostly leave that up to artistic license. They have six fingers/toes on each hand/foot. The outermost two fingers (opposite of the thumb) have greater mobility and act together as a somewhat inferior extra thumb. The entire end of the finger/toe tips have a protective bone plate, similar to nails.

The external genitalia are two mostly separate structures, which I am covering to avoid the area being drawn without clothing (and assumably without the relevant organs). The vulva-equivalent/oviduct-opening/place-an-egg-comes-from is pretty much were and functionally how it is on humans. 

More relevantly, the penile structure is higher than on humans and rests above the pubic bone (the internal part goes over the pubic bone, rather than under). Everything is normally retracted into the abdomen (there is a protective structure it draws into) and does not really leave anything hanging out.

Ange wear clothes more than any other sapient species, and I did not particularly expect you to be doing full anatomical drawings. However, I know it would have annoyed me if you drew an Ange in a bikini and left out the junk because I did not at least mention it was there. You can also draw Ange pornography if you want, but that is up to you.

Gosaa

While a Gosaa can be a blob with their vital organs floating inside and form muscular pseudopods on demand, most of the time the average Gosaa is replicating another creature or combination of creatures to make a practical structure. It is worth noting that they cannot become just undifferentiated cells, even if they can revert or recombine any cells in their body on demand.

They require a variety of organs and a kind of circulation (although the structure changes constantly), so being shaped like a good animal for the environment can protect those organs and help them move more easily. They are primarily opaque, so you cannot see where their organs are at a given moment.

Harg

The facial/skull structure is similar to Ange. They have the human-style flat faces, since the jaw is not intended to be a weapon. The area a nose would be is basically a sheet of bone (under the skin and micro-muscles), same as the rest of the non-orifice-skull. The eyes are significantly larger and faceted. They do not move and it is not possible to tell where a Harg is looking (they technically see all directions equally, but are normally focusing mentally on one thing at a time). Up to you on the angle of the eyelids, but they can close their eyes and do blink to maintain moisture.

The jaw is smaller than on Ange, proportionately narrow and angular in comparison to the skull (by human standards). The mouth is pretty similar in principle to humans, lips covering the teeth and containing intricate micro-muscles for expression.

Their skin is translucent, allowing the muscles and organs to be seen and slightly seen through. The skeleton is partially visible (not very clearly). It is distinctly different than a human skeleton, but accomplishes the same task. They do not have ulna and radius in their lower arms or tibia and fibula in the leg, having only one bone to fill each roll (Ange are the same, but you cannot see it through their flesh). Otherwise I will leave the skeleton up to artistic license.

As for build, they fall into the human male structure on a skeletal level. Unlike Ange, Harg do not pass their offspring through the pelvic opening or anywhere else. Their hips do not widen more than required to attach torso to legs and their widest point is their shoulders.

Their limbs are a bit longer than humans, and the angles and range of their joints are off from human, but I will mostly leave that up to artistic license. They have four fingers/toes on each hand/foot. They do not have any equivalent of fingernails.

Fern like structures grow from their head, shoulders and down their back, although it resembles moss stems in the shorter areas. The ferns on their heads flower and then fruit during part of the year, but otherwise they do not have genitalia.