What was your actual assignment? That will also help for more constructive post-draft critiques.

As it is a draft, a lot of what I say is just minor proofing errors. However, I have given myself free-reign to voice my opinion, wherever and whenever it felt like it wanted to be voiced. Please, don't take it as insulting - I'm sure you won't! It is just an unrestrained thought process. I am, as I said, thoroughly enjoying it. I do like the idea!

Here we go then:

Helen listened to the heavy rumble of the anchor as it unrolled.
I love that the rumble is heavy, rather than the anchor!

It had been a long time since she’d last heard that sound, she and her crew were long since over due some shore leave, and vitally now, some fresh food.
over due==overdue.

I find this sentence too long; I think I'd like a full stop after 'sound'; or perhaps it's just that 'and vitally now' doesn't quite read right. I think something like "It had been a long time since she’d last heard that sound. She and her crew were long since overdue some shore leave and it was now vital, to replenish their fresh food."

Her crew, with their nerves silenced for a while, were shouting to one another as they secured the boat.
Is crew one of those words that can be either singular or plural?

She took another glance through the small panes of the window
Does the window in the captain's cabin have a special nautical name? Sailing folk do stuff like that, after all; I’m sure sheepy would know! I believe the Captain’s cabin is also referred to as the State Room. Just general wonderings, really.

Her tender age, cheerful personality and eager willingness to learn and work soon made her a favourite of the crew who would vie with each other to entertain her and ensure she was well cared for.
the crew, who

She had grown up wise in the ways of the sea and of running a ship, and when she turned 21 her father had no hesitation in giving her her own ship.
Repeats ship - maybe 'her own command'?

She dreamt of him caring for her, treasuring her for who she was, not what she had achieved.
'not for what' instead of ‘not what’ would read better, I think.

She even dreamt of being in his bed, and in her wilder dreams, the ones she had at night when she slipped a finger between her virgin lips she dreamt of being tied with ropes like the ones which lay curled above the roof of her cabin.
virgin lips, she

It was not as if she had not had offers, but they were never ones to tempt her to either leave her ship or share it.
Split infinitive, split infinitive, split infinitive - sorry! Pet hate. ‘either to leave her ship or to share it.’ Please!

As she sat at the table in her spacious captain’s cabin looking at the chart she had a private moment of doubt.
chart, she

She selected a pen and some coloured inks and carefully added the tall imposing castle which she could now see through her window to her father’s old chart.
Ummm - commas round sub-clause, 'which... window'? would make it easier to read, don't know if it's grammatically expected. I find the sentence difficult to follow.

It was a castle straight from the fairy tale her father had told her all those years ago, with small windows, towers, turrets and spires.
fairy tales

Her crew had argued and reasoned with her against this, but finally she simply pulled rank, and gave them permission to complain to her father when they next saw him.
‘she had simply’, I think; and therefore ‘given’ or ‘had given’.

She had agreed that they would replenish the ship which whatever provisions they could find on the island
'with' not 'which'

and then wait for two moons before abandoning hope of her returning.
abandoning... returning. - This is probably just me, but the ing - ing grates. How about abandoning... return?

shook it back into its pot and then lovingly rolled the chart once again and stowed it with the others.
I get the feeling you're notching up quite a lot of 'and then's. Some re-wording or change in punctuation might avoid them.

Taking a key from the bunch which she wore around her waist at all times she unlocked and opened the drawer under her bunk
.

times, she

Her fingers ran over the rich cream silk of the dress she had brought for this moment.
Did you mean brought (with her)? or bought?

A knock on her cabin door and a line of sailors entered carrying pitchers of precious desalinated fresh water.
I actually like this construct, but I think 'With a knock on her door' or some such would probably read better.

the steam lifting the scent of the soap as she inhaled and felt wonderful.
She felt wonderful? or the steam lifted and felt wonderful to her?

Relaxing into the luxury she breathed deeply as her hands took the weight of her cupped breasts. Each one just filling her hand as she ran her thumb down over the soft soapy flesh until catching her hardening nipples between it and her index finger.
luxury, she

'Each one just filled her hand, as’ or ‘Each one just filling her hands, she’.

Some confusion with one thumb but two nipples; also too many ings again. I started playing around with alternatives, but I’m sure you can fix it.

She pushed down hard, first feeling the hardness of that bud and then as she pushed harder feeling a comforting pain as she squeezed and rolled.
Purposeful repetition of hard and derivatives?

Then she released the two captives only to repeat the process, but this time massaging her breasts too as she closed her eyes, sighed and contentedly threw her head backward, and once again experimented with just how hard she could squeeze them.
Long sentence, doesn't read easily. You could try '(...) process. She closed her eyes, sighed and contentedly threw her head backward as she massaged her breasts and once again...' or something like that?

windows of her cabin she stood allowing
‘cabin, she stood, allowing’ (although you could do without the second comma, I expect: depends on your meaning).

the water to trickle down off her body as she rubbed the excess water from her hair.
repeats water - I don't think you need the second one.

Then kneeling on her bed, she bent over and hung her head over the side, brushing first one way and then the other the falling mass as the air dried body into it and her soft bristled brush polished the natural sheen.
Um. Difficult sentence to read. I was not sure if you meant 'brushing' as with a brush (which you obviously did, but I didn't find out until the end of the sentence) or 'brushing' as in moving her head back and forth so it brushed against the bed. Perhaps you could try something like,

Then, kneeling on her bed, she bent over and hung her head over the side, using her soft-bristled brush to sweep the falling mass from side to side. The air dried body into it and her brush polished the natural sheen. (Only this repeats side. And over. Humph.)

It would be more comfortable to not to bother with a corset in such weather,
Too many to's, lol

The light musky floral scent more reminiscent of an elegant dinner party than a captain’s cabin, she dabbed it on, replaced the stopper, took
I know what you wanted to do but it would only work if the scent were not itself the object of the next bit, I think. I think you have to say the scent ‘was more reminiscent’ (and full stop after cabin).

Her chosen deputy was waiting for her and he helped her climb down the ladder into the waiting rowing boat.
Remove ‘he’, unnecessary.

She deliberately did not look back for fear of weakening at the last the moment,
Too many the’s

A shadow passing beneath her boat showed it was rich in fish.
Only one shadow for lots of fish?

She pointed all this out to the same old sailor who was now rowing her ashore as had once playfully taken her hair brush to her.
Hard to read; try something like ‘She pointed this out to the sailor who was rowing her ashore; this was same old sailor who had once…’

The boat crunched over the pebbles and he leapt into the water carrying her shoes and pulled it as far as he could onto the shore.
The objects are getting a bit mixed up. I think it would be easier to read if the shoes were separated out more, for example “The boat crunched over the pebbles and, carrying her shoes, he leapt into the water and pulled it as far as he could onto the shore.”

Lifting her skirts and gathering them up she climbed out into the clear warm water, swayed as she found her footing and then whispered to herself “Here be Dragons”. He knelt down to put her shoes on for her, they bid each other a formal farewell, and then with mixed emotions he took her into his arms and reminded her that she was her father’s daughter and wished her well.
Well, I know it’s a story and he has already taken a certain liberty with her, but this doesn’t sound right for a crewman towards his captain. Just too familiar.


yet there was a dark foreboding aura which hung around it.
I think you could shorten this to ‘yet a dark, forbidding aura hung around it.’ Note – I’ve put forbidding not foreboding, because foreboding as a verb must take an object. The aura could forbode ill, or fill her with foreboding, but it can’t just forbode.

As she approached she was less sure that there would not be dragons, she was even less sure that she wanted to proceed. (…) Her mission and dream would be unaccomplished, she had to proceed.
Can you replace the first ‘proceed’ with ‘continue’ or other synonym?

Feeling her heart heavy she climbed
Feeling her heart heavy, she climbed

the semi circular steps to the door which appeared to be the main entrance. As she lifted her hand to knock on the great heavy door it creaked open revealing a panelled baronial hall,
Replace first ‘door’ e.g. with gateway or similar?

‘creaked open, revealing

complete with a huge fire blazing in the stone fireplace. Apart from the door she had just entered by there was one other door and a stone slab in the middle of the room. Otherwise the room was empty.
Repetitions of door and room.

‘Welcome brave traveller to the end of the world. You now have a choice, once you have decided there will be no turning back, so take time to think carefully. Turn back and leave through the door behind you, and may leave this land safely; go through the door ahead of you and will discover much.’
‘Welcome, brave traveller to the end of the world. You now have a choice. Once you have decided, there will be no turning back, so take time to think carefully. Turn back and leave through the door behind you, and you may leave this land safely; go through the door ahead of you and will discover much.’

Repetition of turn back.

It was a challenge she did not wish to resist, her heart racing
It was a challenge she did not wish to resist. Her heart racing

she walked over to the second door, her hand resting on the handle, and then she pushed.
Still a lot of doors and now hands and handles – not sure how to handle that! lol. I think you could give this more dramatic moment by breaking it up a bit, something like ‘(…) she walked over to the second door. She rested her hand on the latch for a moment, then pushed.’ (I know Word always wants you to say ‘and then’ – but why? ‘Then’ is perfectly meaningful, I think!)

Around the fire were two high backed, winged leather arm chair.
chairs.

The door closed with a solid thud, and then there was silence in which she suddenly realised what she had done.
The door closed with a solid thud, and then there was a silence, in which she suddenly realised what she had done.

Her muscles tensing and her palms sweating she breathed deeply to control her rising panic.
sweating, she breathed deeply

“Welcome, do come over here and sit by the fire so we can chat” said the disembodied voice.
“Welcome. Do come over here and sit by the fire so we can chat,” said the disembodied voice.

Her legs heavy, she compelled them to move, terrified.
I have a feeling this implies that her legs are terrified. Perhaps it should be ‘Terrified, she compelled her heavy legs to move.’ Or ‘Her legs heavy with terror, she compelled herself to move.’ Or such like.

There was an eerie stillness which framed the sound of her footsteps on the wooden floor and the murmour of her skirt.
Murmur.

“Well you are a sight for sore eyes” he said, chuckling to himself.
“Well, you are a sight for sore eyes.” he said, chuckling to himself. (Would just ‘he chuckled’ sound better? Or is chuckling quite the right noise? I assume you want him still to be, well, imposing, even if he is putting her at her ease. Chuckling just seems a bit too jolly. Mind you, the only alternative I thought of was the long-winded, ‘laughing gently to himself in appreciation.’

Whilst I can’t say you’re a surprise since I’ve been watching you
Whilst I can’t say you’re a surprise, since I’ve been watching you

Her curiousity grew, she did not know what she had been expecting, but it certainly was not such a gentile everyday greeting.
Her curiousity grew. She did not know what she had been expecting, but it certainly was not such a gracious, everyday greeting.

Gentile is definitely not the right word!! And would it be both gracious and everyday?

He repeated his invitation, indicating the chair the other side of the fire “please, do take a seat”.
He repeated his invitation, indicating the chair the other side of the fire. “Please, do take a seat”.

As it is, you have chosen the more interesting option, it will not be an easy one for you, but something tells me you have the strength to unlock what you seek.
As it is, you have chosen the more interesting option. It will not be an easy one for you,

With that he waved his hand and she suddenly noticed a small table between the chairs with a couple of glass and a jug
glasses

As she drank the lemonade she felt refreshed in the way a swim in fresh water refreshes at the end of a long day, she sat back in the chair and smiled back at him, and started to recount her tale.
at the end of a long day. She sat back

But looking at his eyes as he watched and waited she was not so sure. Perhaps she should be careful what she should think. He chuckled.
But looking at his eyes as he watched and waited, she was not so sure. Perhaps she should be careful what she thought. He chuckled.
(that’s a good chuckle, lol)

Taking one last look at a particularly spectacular bird she hurried to catch him up.
bird, she hurried


“Oh yes” he replied with the wry smile, “well one dragon, one rather lonely dragon truth to be told.”
“Oh, yes,” he replied, with the wry smile. “Well, one dragon; one rather lonely dragon, truth be told.”

not to say confused about the easy way
confused by, I believe

very rarely does he breath fire, yes, he can,
very rarely does he breath fire; yes, he can,

The long polished table decorated jewel encrusted silver vases holding flowers akin to lilies which filled the air with a heady scent.
The long, polished table was decorated with jewel encrusted silver vases, holding flowers akin to lilies, which filled the air with a heady scent.

How about something more visually evocative as well, ‘…silver vases. Out of these cascaded bright flowers…’

A banquet had been laid and after months of careful rationing of all fresh food to a sailor’s eyes it appeared to have come straight from the Garden of Eden.
food, to

His eyes cut her short. “You want?” he repeated with an emphasis on the want.
I think the typography could do the emphasis for you here, “You want?” he repeated. And is he being stern, for example? Cold? Chilling?

She felt like a child again and stuttered “I would like to sit next to you, if I may.” she corrected.
Don’t need ‘she corrected.’

“And I would like you to sit next to me too”, he nodded.
“And I would like you to sit next to me, too,” he nodded.

And I hope that I will be able to persuade you stay a little while once you have rested from unlocking the portal, it would be so nice to enjoy your companionship.”
And I hope that I will be able to persuade you to stay a little (…) portal; it”

Eventually she spoke through the frozen time “how do I unlock the portal?”
Eventually she spoke through the frozen time. “How do I unlock the portal?”

('the frozen time' - lovely!)

She lifted her glass to her lips and sipped, and then drank, blushing when she suddenly realised that she had just drank best part of a large glass as though it were water.
Sipped, then found she’d drunk most of it? How about sipped, was enraptured by its flavour or such, sipped and sipped again…

He chuckled at her, once again as though reading her thoughts “I see you find the same.”
Hmm. Chuckling again.

As they ate she became intoxicated with the range of fresh and powerful flavours, her senses seeming to heighten the longer she was in the castle. Her senses and her emotions; as her plate emptied her attentions became even more focused on her strange host.
The semi-colon seems to be in the wrong place here. It would make more sense as “the longer she was in the castle; her senses and her emotions. As her plate emptied…” But still – her senses and her emotions what?

Picture after picture formed in her mind as she listened, but fascinated as she was, her eyelids got increasingly heavy until in her dazed state it seemed the most natural of things to feel him to pick her up and carry her from of the dining room and along another corridor to a room which a had a large four poster bed in the middle of it.
Woo! Loooong sentence…

He placed her gently on the bed, pulled a cover over her and bent down to kiss forehead tenderly.
her forehead

Her first land bed after so many moons felt strange. She missed the creaking of the ropes, the footsteps and sailor’s talk, the wind or lack of wind.
sailors’ talk

She normally lay in bed doing a quick mental check that all was well, but instead she listened to the only sound she could hear; his breathing as he sat on the edge of the bed holding her hand. As she slept she missed hearing the soft whooshing of a tail along the wooden floor followed by the dull thud of her door being closed.
I think you need a transition here – you were just talking about her missing the sounds of the ship; but then you use missing in a different sense. It is difficult for the reader to understand your meaning first off, which is a shame. Also, she is awake in the previous sentence, and the reader doesn’t know she is now asleep.

You could try breaking the paragraph between the two sentences; you could try adding a ‘she drifted off to sleep’ in between the two of them; that sort of thing. I think ‘As she slept she also missed’ would help, too.

“Oh, don’t worry, that is all I removed, was far too nice a dress to sleep in,
“Oh, don’t worry, that is all I removed, it was far too nice a dress to sleep in,

“Well, I am pleased you feel that way, not only for my own ego, but you have a tough day ahead of you.” Now he had her full attention, pulling the bedclothes around herself, she sat up in bed. “I had a feeling yesterday you could read my thoughts. Can you?”
I think you need to put her sentence on a new line, otherwise it looks like a continuation of what he was saying.

“Well, I guess that was a bit of a give away, but you can’t blame me for trying to impress a lady as beautiful as you. And you need not worry, anytime you tell me to stop doing so I will. I may not be quite what I seem to be, but I am no cad.”
Would this olde-worlde, beautiful, mysterious man really say ‘that was a bit of a give away’?

stop doing so, I will.

which is actually just another world is closed to your people by a magic which was created when the worlds divided.
world that is closed, I think

“This is no ordinary level of pain you are going to have to experience, I am sure
“This is no ordinary level of pain you are going to have to experience. I am sure…

Those cries would not be enough to more than dent the portal. You have my word that although you will feel pain which is sometimes far beyond your imagination you will not suffer any long term damage.”
I can’t believe I’m actually accepting a split infinitive… maybe someone else won’t. No, no I can’t – ‘to do more than’ gets round it.

pain that is (again - I think!)

imagination, you

She might have replied, if she was not too busy feeling trapped by a strange
She might have replied, had she not been too busy feeling trapped by a strange (or, if she has not been)

“No, and when you chose to come in and not return to your ship you committed yourself to going through with this.
not return to your ship, you

Rocking her gently he whispered reassuring words,
Rocking her gently, he whispered reassuring words,

slowly calming enough to prepare herself.
Doesn’t quite work; you could try, 'slowly calming enough to be able to prepare herself', or 'slowly calming enough to prepare herself for the ordeal'.

her hand and helped her to feet, and helped her into a soft robe
and helped… and helped

the night before to a heavy wooden gothic door.
the night before, to a heavy wooden gothic door.

It looked as if it should have creaked as he opened it, but it swung effortlessly revealing a wide torch lit staircase curving downwards.
effortlessly, revealing

As she paused nervously she he reassured her once again
An extra she crept in there. nervously, he

At the bottom of the stairs was an iron bar gate through which she could see what she instinctively knew to be a dungeon.
iron bar gate, through

It was not damp, it was also lit by torches, and heavy with equipment the uses of which she tried not to think about.
Why ‘also lit’? And… can she really see it is heavy with equipment at this stage? Would it not just be ominous with dark shapes she can’t quite make out yet? (or is that just the way I’d like it to be!!)

Now I have to go and do housework! How boring... would much rather carry on doing this...