This story will involve sex between humans of both sexes and various aliens of various sexes. Everyone involved is at least 18(or whatever the equivalent is on their planet!)
Inspiration comes from numerous writers including of course Edgar Rice Burroughs, but also as things develop, Robert Heinlein, Philip Jose Farmer and Herman Melville.
***
He could see the light of Napris fading as he ran through the trees. He had to catch the Rokken before first nightfall. If he failed she would not die, but she almost certainly would not want to live. He pounded on, his bare feet thudding on the forest floor, sweat forming a glistening sheen as it ran down his back. The short leather kilt that was his only clothing swung on his hips, chafing his luminous blue skin as he ran.
[[Blue skin? WTF]]
In his each hand he held a spear, long, straight with barbed points. Across his back was a great sword, his image of power among his people, for no one else could handle a blade of such weight with his dexterity.
Suddenly, through the trees he saw them. Three Rokken, one with the girl slung over its shoulder, all three of them running steadily, their lumpen hairy bodies much more effective than they appeared. Even so, he knew he had them now. He quickened his pace, hefting the spear in his left hand as he ran. He was gaining on them. Suddenly he burst into a clearing around a rocky outcrop. They heard him break through and turned, snarling. Without breaking step he hurled the spear in his left hand. It flew though the air to take one of the Rokken square in the chest, driving through its lumpen blue flesh to impale it on the tree behind. The Rokken with the girl, threw her to the ground and the two remaining charged towards him. He threw the second spear and it pierced the creatures throat. It flew backwards to land in a pool of stinking water where it died, screaming.
The final Rokken turned to grasp the girl and flee before it met the same fate as its companions, only to be met by a smashing blow to the side of the head from a stone thrown by the girl, felling it to the ground.
"Quickly" screamed the girl. "First night is almost upon us. We must get into that cave until Mura rises for second day. "
Without stopping, he ran forward, pulling the first spear from the tree like a pin from a pin-cushion, hurling it into the cave the girl had seen. A great roar echoed from it before a huge wolf like creature burst forth. Snatching up the second spear he ran forward and thrust it without pausing into the creature's breast. Leaving the beast in its death throes, he seized the stunned Rokken by the hair on its back and ran on into the cave, closely followed by the girl.
[[WTF?]]
Once inside the cave he paused to take his bearings. The cave ran deep into the rock. Towards the rear was a pool of water, behind which it bent to the right. The water in the pool glowed milky white and steamed gently. There were signs of occupation by the pool where there was a pile of animal bones, but otherwise it was empty. He turned to face the entrance. Just outside was a huge bush. He stepped out and seizing it bent it down to obscure the entrance.
"That should be enough during first night" he said. He turned to the girl, who stood before him, naked as he was apart from her short leather kilt. Her body was firm and round with large breasts and wide hips. He stepped towards her, the Bloodlust rising in his veins, his phallus thickening and rising beneath his kilt. He stripped the kilt from his body, throwing it to one side and taking the girls arms in his huge hands.
"NO!" she cried. "I know the Bloodlust is upon you, but I am not yet ripe and if you plant your seed in me I will be damaged and your soul will lose many levels of advancement.
"I care not," he cried. "I will have you for my sword cannot go unquenched when my blood is high."
"You can take her" said the girl, pointing at the hapless Rokken cowering against the cave wall.
He turned as the girl pointed. The Rokken was indeed female, and beneath the dirt and matted hair appeared to have all the attributes of a Human female.
"I cannot take that! It would be like rutting with an ape."
"No, she said. They can speak and have some understanding of our ways. My father thinks that they are fallen Humans, but because of some great disaster were reduced to living and mating with the great apes. If you plant your seed in her, your offspring will be as Human as you or I because you are a Hero."
"Lord, I would give myself to you if I could, but for both our sakes you must quench your Bloodlust in this sad creature, not in me. I will cleanse her in this pool before you take your pleasure."
The Hero paused. "Do it, but quickly, for my Lust is high and I fear I will soon be unable to control it."
The girl took the arm of the cowering Rokken, leading her to the milk white pool, walking with her into the water. At first the creature seemed afraid, but as the warm water enveloped her body she relaxed and allowed the girl to rub the stains from her flesh using clumps of moss gathered from the pool side.
"My Lord" said the girl "the water is warm and has healing properties. Why not bathe your body too and refresh yourself as I clean this creature."
The Hero realised his skin was torn and scratched by his pursuit of the girl and her captors and stained by many days travelling before that. He stepped into the water alongside the girl and the Rokken, now cooing gently as the warm milky water soothed and calmed her. As he bathed, his Lust began to rise again. The Rokken was not the lumpen dirty animal he had pursued for hours. Her skin was now an iridescent blue, paler than his own but with a soft glow as if it lay over another colour. Her body hair was no longer matted but soft white and downy across her body. Her breasts and belly were bare. The hair on her head was very dark blue curls, much darker than her skin. It continued down her spine, growing longer and straighter, reaching to just above the cleavage of her buttocks.
As he watched the girl smoothing the Rokken's body, his phallus finally awoke, stretching out before him, writhing and curling like the body of a snake. The girl and the Rokken watched it in fascination as it twisted before him, growing ever longer and thicker. Without thinking, the girl stretched out her arm and the phallus began slowly to wrap itself around the forearm, shortening and pulling the girl towards him. Her mouth fell half open, face flushing, lips thickening with desire.
"O Lord, I cannot, but I so wish it."
His phallus slowly unwound itself from her arm, its head towards her as if watching. Meanwhile the Rokken had fallen on all fours, equally fascinated by the twisting winding thing in front of her. He turned towards the the Rokken female and realised that her body was also responding. Her mouth was open, her face glowing while the longer hairs on her back, lifted and sank backwards, rippling up and down her spine. He stepped forwards and seized her, quickly turning her body around and roughly parting her legs as she knelt before him. Reaching between her thighs he found her slit, already swollen and moist. He fingered her and her body arched, the spine hairs standing erect. His phallus snaked towards her, plunging of its own volition deep inside her, She shrieked, not with the voice of an unthinking animal, but that of a woman in ecstasy. He thrust his hips forward, plunging deeper into her body, grasping her breasts in his hands, pulling her body upwards as he continued to thrust. Her muscular body pushed back against him, he could feel her buttocks against him and he gasped in pleasure as he came, pumping his seed deep into her womb.
He collapsed back into the water, keeping inside her so that he lay on his back with her on his stomach. Her body was still shaking with orgasm, the hair on her back vibrating against his belly, the strange sensation keeping him firm and hard, although it was slowly pulling back into itself, pulling the head back. She shuddered as it pulled back, his huge girth stretching her beyond anything she had ever experienced.
He looked across at the girl. She was lying back in the water, her legs apart, fingers deep inside herself, panting and breathless as she came down from her own orgasm.