There it was - the seventh globe. He picked it up and looked at the swirling images of friends he had met in his seventh incarnation. The most important of them were Mel, who had been with him at the start, and Ace who had joined him later.

Enemies swirled within the glass, too. The Rani, Davros again and his infernal creations, Cybermen gleaming menacingly.

But it was none of those he was destined to face this time. He turned to look at the glass case where the next key should go, opening this seventh door.

“Svartos,” he whispered to himself, the sound of his voice nevertheless loud in this silent place where he alone trod. “The Iceworld.”

The holograph of the tidal locked planet, one hemisphere permanently frozen, the other a boiling desert, hung above a pattern made of crystal, but resembling the patterns made by ice solidifying on glass – the fronds and ferns attributed to Jack Frost and such mythological beings by the fanciful.

There was, of course, a gap in the centre of the pattern. It was the shape of a bowl with a stylised ice crystal shape on the base – three diamonds interlocking – the symbol of the Svartosan people.

That meant he was to visit Svartos before it became Kane’s prison, when it had a population of very creative troglodytes who lived and worked within the ice caves. A plague had wiped them all out at least three centuries before those events. It was an empty, dead world when it was chosen for that sinister purpose.

He trusted the TARDIS wouldn’t land him there in the middle of the plague, otherwise his destination was set.

The destination was in the cavern of the singing trees, already a considerable depth below the thick permafrost on the dark side of Svartos. The Doctor stepped out and appreciated the natural glow from the luminous quartz in the cavern walls. It bathed him in a soft light that came from all around him and cast no shadows. The ‘singing’ was caused by air currents that blew through these upper caverns. The ‘trees’ were fantastic accretions of crystal formed into the most delicate of stems and fronds like giant white ferns. The air currents moved them very gently and caused a musical sound like hundreds of wind-chimes all playing at once. It was surprisingly tonal. He could listen to it all day if he didn’t have a mission to get on with.

The cavern and the ‘trees’ were formed by nature, but the Svartosans had cut steps to make the way down into the lower levels easier. The Doctor followed those steps down into what would have been a far more ambient place when the people lit fires that warmed a series of flues and pipes keeping the frost at bay.

Those fires hadn’t been lit for a long time, now. This was a cold place. The gravity globe he lit as he entered the lower passageway reflected off frost covered walls. His feet crunched on layers of ice that had never melted.

This planet had a core of ice. Even the heat of the sun-baked permanent daylight side didn’t penetrate far enough to alter that. Iceworld was truly named. Given enough time, these tunnels would probably fill with ice and the very existence of the Svartosan troglodyte race would be forgotten.

Not yet. The Doctor stopped and looked at a frost covered alcove. There was some kind of glass beneath the ice. He cleared the frost away and peered into the dim space behind.

There were two bodies there. They were a male and a female. He could tell because they had been mummified in the cold, dry air. Their skin had turned to a deeply tanned leather. Their eye sockets were empty and sunken and their long fingers bony and brittle. Rags of clothing remained on their short, slender bodies.

They must have lain together knowing that they were dying, he guessed. They had sealed their sleeping alcove to protect any yet uninfected people.

It had been a fruitless hope. The entire population had died. The planet had been quarantined long before then and it was avoided for a generation.

He might actually be the first person to set foot in these passageways since the tragedy. Eventually a party of anthropologists did come and look and confirmed that the race was extinct. They left the bodies where they were in their self-made tombs, and of course, the ice did eventually close up the passageways long before Kane was exiled here. The Svartosans were buried in their subterranean community, never to be seen again.

The thought saddened him. But it was a natural disaster. It was not caused by any evil hand, any malicious plan to destroy them. It was something that even he, under pain of death by the Time Lord Council, would have been forbidden to interfere with.

And he wouldn’t have interfered. His mission had always been to prevent tyranny and injustice, not plagues.

He told himself that as he passed more and more of these alcoves. At one point he came into a wide place that had been cut almost square and rose up to four storeys – high rise sleeping alcoves, each closed and frost covered, each containing a long dead, mummified family of Svartosans.

Below that level, where they had slept, there was a great communal hall where the Svartosans had eaten. There was a huge table there, hewn out of the rock. It was covered in ice, of course, but there were still cups and bowls on it, frozen in place. They looked as if they were made of ice themselves, but they weren’t.

He prised one of the bowls free with help from the sonic screwdriver and examined it carefully. This was what the Svartosans had once been renowned for – rock crystal ware. These on the table were simple everyday utensils without decoration, but they had been made by patiently shaping pieces of rock crystal mined from the rocks around them. The cups were less than a few millimetres thick and as clear as blown glass. The bowls were smoothly shaped and curved inside and out.

The Svartosans had traded in far more intricate examples of the craft. Rock crystal mounted in silver imported from elsewhere in the galaxy was prized by the wealthy who liked to show off their affluence. A full dinner service would literally cost a king’s ransom, and Kings and Emperors, Presidents and Predicators placed their orders. All over the galaxy museums contained fine examples of ancient Svartosan workmanship.

Somewhere in the labyrinth of passages and numberless caverns would be the Svartosans own treasure trove of their very best work, made for the glory of the mother planet within whose bosom they lived.

That treasure trove was what he was seeking. He was almost certainly the first to do so. Later, the halls would be plundered for their treasures. It would be a bit of a scandal at the time. Some of the pieces would go into museums, but the vast majority of it would end up in private ownership, selling for huge sums at auction and making tidy profits for what many people regarded as grave robbers.

Of course, he was here very much for the same purpose. He was going to take one of the treasures for his own use. Did that make him a hypocrite? Possibly. But he needed the bowl with the seal on the base to complete his quest. Later, he could bring it back.

Or not. What was the point? It would only end up in the possession of somebody who cared nothing for it except its auction price. He, at least, valued it for its beauty, for the exquisite skill it took to make such a thing.

There were pieces of crystal in the walls of the passages he made his way through. He extracted a piece with the sonic as a lever. It was the size of a salt pot, an uneven but angular shape, the facets rough but nevertheless catching a glint from the gravity globe that moved along in front of him as he walked.

A Svartosan master craftsman would take a thing like this and carve out the middle until it was smooth, then the outside until it was only a millimetre or so thick before etching it with patterns so intricate they would make the authors of the Lindisfarne Gospels weep with envy. It would be polished until it shone like glass, only it was far stronger and much purer. Silver fittings would be added to turn it into a salt cellar or a finger cup or a perfume bottle, whatever the craftsman saw within this piece of formless crystal.

The monks who lived on the mountain near his home on Gallifrey had the patience to watch a flower grow from a seed to a bloom, then die away and form its own seed cap. He had never had such patience. He would sooner invent a time disrupter that would make the flower grow in a few minutes.

He tried to imagine himself patiently carving this piece of crystal into a thing of exquisite beauty. The image refused to form in his mind. He couldn’t have done it. He would have given up within the first hour, let alone the days it would have taken even for such a small item.

The Svartosans were superior beings in that respect. He took his hat off to them. Well, he would have done if he had a hat. His seventh incarnation was a hat wearer. He would have done so.

He was rambling. He admitted as much as he moved through the seemingly endless tunnels and stairways that brought him lower and lower within the Svartosan subterranean world.

He came to another wide cavern which had obviously been the main workshop. A wide table much like the one where the people had eaten was littered with tools and half finished pieces of crystal-ware. The Doctor looked at a vase that was already hollowed out perfectly and was ready to have the decoration added to the outside. The craftsman had become sick before he could complete his work. Many other pieces were left unfinished, sharpened tools never again to be taken up by their owners.

“I’m sorry,” The Doctor whispered. Even more so than when he looked at the mummified bodies, or when he walked through the communal hall where they must have spent so much of their free time, he felt the tragedy of the lost race as he looked at the workplace where they produce such magnificent objects.

He picked up one of the fine, diamond edged knives and tried to carve into the piece of crystal he had taken for himself. He managed to scratch a rough line into it before he gave up.

Definitely no patience.

On again, down still further. The treasure houses were in the very deepest levels, of course. They were part vaults and part temples. The Svartosans worshipped the planet itself, a spirit they believed was in the very rocks around them. They would bring offerings of the best rock crystal treasures, giving back to Svartos what was taken from her when they mined into the rock.

It might seem like a peculiar sort of religion to some, but The Doctor thought it was perfectly fine. It was quite harmless. They didn’t sacrifice their children or perform any disturbing rituals. They simply made beautiful things in honour of their mother goddess who gave them shelter. What was wrong with that?

He clung to his piece of crystal and wondered if he might come back again before the disaster and have it carved properly. These silent, echoing, freezing cold places were a sad remnant of a wonderful people who were no more. He felt strongly that he wanted to see them when they were a thriving community, before the disaster that befell them so suddenly and so very completely.

But for now he had a mission to complete. He kept on going, leaving behind the workshop and continuing deeper into the mantel of the planet. It was colder and colder, but his body adjusted automatically, keeping his blood at a steady sixty degrees. He was in no danger of freezing in the foreseeable future.

At last he reached the very lowest level – At least as far as he could make out. Here, anyway, there were no more staircases.

And for the first time, he came to a door barring his way.

It was a big door made of a single sheet of thick, completely opaque rock crystal. It was bolted, but not locked.

That was strange. The Doctor wondered why, if this was the treasure house, it wasn’t secured by something that would hold back looters. The bolts were strong, and they were frozen in place, but they were relatively easy to deal with. He used the sonic screwdriver to slowly melt the ice before simply pulling the bolts back.

He pulled open the door and stepped inside. This was not the treasure room, but it WAS a treasure in itself, the temple where the Svartosans worshipped their mother planet. It was a beautifully decorated cavern, its walls adorned with stained rock crystal in the way humans put stained glass in their cathedrals. The natural phosphorescent glow in the walls lit the patterned crystal and created a place of vibrant colour.

In the middle of the cavern was a kind of altar, a large round rock carved and shaped and edged with silver and more coloured crystal.

The Doctor understood now why the door was bolted like that. It wasn’t to keep anyone out, but to keep someone in.

“Hello,” he said to the small, elderly man who turned from the altar and stared at him in alarm and astonishment. “Please, don’t be scared. I mean you no harm. I’m The Doctor. Do you have a name?”

“Fren,” the small man replied. He was a Svartosan, of course, no more than five foot tall, with slender limbs and an elongated skull. He was wearing a crimson and saffron robe with a skull cap of the same colours and was carrying a highly ornamented bowl containing rock crystal models of fruit, delicately hand coloured with natural paints.

“I… I must finish making the offering,” he said. “Please be waiting.”

“I will certainly do that,” The Doctor promised. He stood quietly and watched as the little old man finished the ritual that must once have been performed before a congregation of his fellow Svartosans. Now he kept it up all alone, perhaps out of devotion, perhaps because there was nobody left to tell him to stop.

When it was done, he turned and beckoned to The Doctor. He led him through a short tunnel to a living space where he gave him a crystal cup of cold, pure water and a plate of dried, spiced fish to eat. He was accepted as a friend. He ate the food with Fren before asking his questions again.

“I have been here since the tribulation began,” he said. “I was not a priest, then, only an altar server. I was seven years old and apprenticed to the priest, Grier. When the sickness began our leaders ordered strict segregation. Nobody was allowed to gather in the temple even if they did not seem to be sick. Grier carried on the rituals and I helped him to do so. Many died and their bodies were closed in the places where they lay.”

“To try to stop the spread of the disease, I suppose?”

Fren nodded.

“But it didn’t work. More and more sickened and died. None were spared. I was here in the temple when my parents died. I remained here. When our leaders died, when there was nobody else left, Grier told me to keep up the rituals and remember, and then he went outside and locked the door.”

“Remember… the lost people of Svartos?”

“My people,” Fren acknowledged. “I have grieved for them long ago. It no longer causes me pain. I did as Grier commanded me. I went on with the daily rites. I fished in the river that flows beneath these caverns. I ate and slept and kept up the rites, day after day, year after year.”

He must have been here for at least sixty years, The Doctor reckoned. Maybe more. He had been a child when the old priest locked him in here, giving him a chance of life, but in long isolation.

“When I am gone, there will be nobody to perform the rites. The heart of Svartos will freeze forever.”

“Yes, I think it will,” The Doctor agreed. “You intend to stay here until you die? You don’t have to. I have a ship. I could… I could take you somewhere else, where you could be with people.”

“There are no more people of my own kind left,” Fren pointed out. There is no reason to be among any other kind of people.”

That made sense in a sad way, of course. The Doctor nodded.

“The treasures of Svartos are legend. People may come with base intentions – to take all the beautiful things your people made.”

“When I am gone, there will be no use for the treasures of Svartos. Let them be taken.”

“Svartosans don’t believe in an afterlife, do you?” The Doctor asked. “There is no heaven or hell for you?”

“We sleep in the bosom of Mother Svartos for eternity,” Fren answered. “When my time comes, I will embrace her willingly.”

“There is nothing I can do for you, is there?” The Doctor said in a resigned tone. “I had a mission here, a favour to ask. But there is nothing I can give you in return, so I do not have the right to ask.”

“You are a good man,” Fren said. “I feel that in your soul. You come here with respect for my silent people and the heart of Svartos.”

“I hope I come to any planet that way,” The Doctor answered.

“Ask your favour.”

“I need to borrow one of the treasures… a bowl this big, this deep, with the symbol of Svartos embossed on the base.”

“I know it,” Fren said. “Come.”

He brought The Doctor along another tunnel and down more steps. It was VERY cold here and there was a sound of running water – that river Fren spoke of from which he had caught the fish he had eaten every day of his life as the last priest of Svartos. Before they reached the river there was another great cavern.

Here, at last, was the treasure cave. It was more magnificent than The Doctor had dared to imagine. The finest pieces of exquisitely carved rock crystal set in silver and gold were placed on shelves that reached to the ceiling, on wide, long tables, and in alcoves cut into the walls themselves. Every surface was covered in the beautiful things made by the Svartosan craftsmen for a millennia. Jugs and ewers, vases, goblets, bowls and basins of all sizes and shapes. Besides the practical items there were delicate sculptures of fish, their eyes made of diamonds and their scales picked out in precious metals, and miniature singing trees with carefully hand carved fronds of the most unbelievably delicate and intricate detail.

On the open market these were worth as much as a whole solar system. The treasures that eventually reached the open market would fetch several fortunes for those who took possession of them.

While the one man who could truly claim ownership lived on fish and water.

“This is the object you seek,” said Fren, reaching for a silver edged bowl with a perfectly smooth inside and a base etched with the symbol of Svartos. It had finely detailed figures etched around the outside. The figures depicted the daily ritual of offering in the temple when there was a whole procession of Svartosans, young and old, to take part. The Doctor looked at the images solemnly.

“I only need to borrow this,” he said. “I will get it back to you. I promise.”

“No, it is a gift,” Fren assured him. “My father made that bowl before I was born. Take it in remembrance of the people of Svartos.”

“But isn’t there anything I can do for you in return?” The Doctor asked. “I am not a plunderer of treasure. I wish I could pay you.”

He searched in his pockets. Was there anything of value he could give to Fren? There was nothing worthwhile.

He pulled a packet of sweets from the blazer pocket. They were sherbet lemons. He offered the bag to the little man who had eaten nothing but fish for as long as he could remember.

“This is a really pathetic offering,” he admitted. “But they’re yours if you want them.”

Fren tried a sweet. He smiled broadly as the sour-sweet taste filled his mouth. For several minutes he could say nothing. When he had sucked down enough for the sherbet to escape a very satisfied ‘oh’ escaped from his lips. After that he kept sucking until the sweet was a mere sliver that broke up on his tongue.

“My friend, this is a delight. I thank you. Please take my gift to you.”

And that was it. Fren brought him back to the Temple, and the door that had been closed for so long. The Doctor shook his hand and then stepped out into the corridor.

“Put the bolts across again, my friend, Doctor,” Fren told him. “I will resume my solitude. Each day until this packet is empty I will eat one of these delights in remembrance of your visit. May you remember the people of Svartos for much longer.”

“I promise that I will,” The Doctor said. He closed the door and bolted it. Then, for good measure, he took out his sonic screwdriver and put a deadlock seal upon it. One day, at least fifty more years from now, when Fren was long dead, the treasure hunters would come. But why should they have an easy time of it? Let them struggle to open this door and find what they sought.

He made his way back up through the levels of Svartosan society, through the workshops, through their communal halls, through the place where they slept in the bosom of their mother world. He made his way up to the cavern of the Singing Trees where he left the TARDIS. He felt both elated by his contact with the last Svartosan and very, very sad. There was nothing he could do about the past and still less about the inevitable future. He railed against his impotence, but it was one of those things that he had to accept, just like the death of his own people or the end of the universe itself in the fullness of time.

He brought the bowl back to the nowhere place with the black doors that held the key to his very lives. He walked through the six open doors and approached the seventh. He placed the bowl in its place in the middle of the crystal pattern. As soon as it slotted in there was the familiar click and soft noise as the seventh door opened before him.

He stepped forward once again, wondering what test lay ahead of him this time.