It's hard to believe I've lived this long. I remember calculating once that, if all went well, Ben and I probably had perhaps sixty or seventy years to live. If all didn't go well – which seemed much more likely, considering how many near-misses we had had lately with griffins, elephant-lizards, volcanoes, and so on – we would probably get killed much sooner. It's strange to think that nearly everyone I knew then is now dead – except for Mizell, who I'd thought was dead, and Atticus and his family, who are undead. Even Atticus looks older now – like a human of around thirty, I suppose. He certainly couldn't get away with hanging around a comprehensive school posing as a Year Thirteen these days.

As it turned out, Ben and I had seventy-two years together, most of it working in at Mimameiđr, the reserve for endangered fantastic beings that Ben's parents had founded. In the many years we had worked in crypto-conservation, we had helped many species back from the brink of extinction, including pegasi and krakens, and even unicorns, who we had thought were already extinct. We had had all kinds of what Ben thought of as adventures and I thought of as trouble. We had seen seawater-powered aeroplanes become the most popular form of transport of the twenty-first century (with only a fraction of the pilots even guessing that their inventor was a troll). We had found my brother Mizell [see The Other Homunculus by Avrel the Teller]. I had helped to bring up three generations of Greenbloom children, as well as Atticus's adopted children, who by now all looked thirteen, regardless of what ages they had been to start with [see One Wild Ride by Evilkat23]. Vampires don't age quickly once they hit puberty, which is why there are so many more teen vampire romances than books about vampire toddlers. Atticus was going to have a house full of teenagers for a long time.

By now, Ben was becoming very deaf and could barely walk. What remained of his hair had gone from being as black as a raven to as silver as a dragon. He could no longer remember what had happened a few minutes ago, but he always remembered who everyone was, and the adventures we had had years before.

I tried to talk to Mizell about what was happening: about the likelihood that I would die, too, when Ben did. I had been horrified the first time I read it, but the first time we had actually seen this happen to a friend of ours, a female homunculus called Rosa Pinkhair [see It's Never Easy by Evilkat23], it just seemed natural. Rosa had such a close link to her creator, Esmeralda, that she could feel when Esmeralda was ill or injured, even if they were many miles apart at the time. But then, Rosa had been actually made from Esmeralda's sperm (since Esmeralda identified as a woman but was biologically male), rather than by transfiguring insects, as Mizell and I had been created, or implanting an animal's heart into a clay doll, like our friend Mouse. Rosa's bond with Esmeralda was inborn and involuntary; my relationship with Ben was something that I had chosen.

I knew Mizell thought I was insane to fall in love with so short-lived a creature as a human, and to become mortal for the sake of one, but I wanted to explain why it had been worth it. I wanted to tell him that my friendship with Ben had helped me become a person again, when I had turned into a creature almost as despicable as Nettlebrand himself: a thing programmed to serve, just as Nettlebrand was a thing programmed to kill. I wanted to apologise to Mizell for the way that, when we'd finally found each other again after hundreds of years apart, I was going to leave him.

But whenever I tried to talk about it, Mizell would just shrug and say, 'It's your decision,' and change the subject. So I tried to work things out on my own. If Ben and I died at the same time, would that mean we would be together in whatever happened after death? Did homunculi even have souls? One book I had read seemed to suggest jokingly that we did, and should be baptised, but it turned out that the author wasn't using the word 'homunculus' to mean artificial humanoids like us, but embryos, or even sperm. He was responding to the Catholic Church's giving permission to baptise babies before they were born, in case they didn't survive birth, by saying that in that case, they might as well play safe and baptise a man's gonads before he has ever had sex, to make sure that his sperm go to heaven. It was a funny book, but not exactly helpful.

At any rate, one evening when I had finished updating a report on phoenix incubation, I came in to climb up to the wooden house Hothbrodd the troll had carved for me, standing as it always did on Ben's bedside table. Ben seemed to be already asleep, so I decided not to disturb him by climbing onto the stack of pillows that propped him up and waking him up to say goodnight to him. At least he wasn't struggling for breath tonight. Then I realised that the thing on the bed was no longer Ben. It was as still and cold as a wax statue. I climbed up the sheets to burrow my face into the pile of pillows next to my friend, and wait to die.

When I looked up, we were in a desert somewhere, under a black sky. I couldn't see any moon or stars, but somehow our shadows stretched out, long and black, on the silver sand beneath our feet. Ben, who was walking a short way ahead of me, seemed to be a young boy again, the way he had been when we first met. I was human-sized, the way I briefly had been once as a result of a spell [see Out Of The Frying Pan by Evilkat23], except that this time it didn't feel strange or confusing. Here, it just seemed normal.

Ben caught sight of a long-nosed, wild-haired shadow, and turned, saying 'Barn – Twigleg? What are you doing here?'

'We're dead,' I said.

'I know. I meant, why? I knew I was dying, but I didn't think you were even ill! I was wondering whether I'd see Barnabas and Vita again, or Slatebeard, or if I'd even meet my biological parents. They died when I was three, and I don't really remember them. Did –did something terrible happen to you?'

I realised that I had never actually explained to Ben before that loving him meant I had to die when he did. When I had transcribed the information about homunculi from Barnabas's notebooks and the collection of old bestiaries onto the database on fantastic beings, I had left out that detail, because I didn't want Ben to read it and worry.

I didn't know how to talk about it now, and have to explain why I had never mentioned it before. This was the most awkward conversation we had had since one night when Ben was fourteen, when he didn't want to talk about missing Firedrake so much that he was planning to leave the Greenblooms and go and live with the dragons, and I didn't want to talk about missing my brothers so much that I had tried to persuade Ben's science teacher to create a homunculus so that I wouldn't be the only one.

At least then, I had been sure that, wherever Ben went, I would go with him. But later, when we'd gone back to visit the castle where I was created, and we'd found another derelict castle where Mizell was now living, Mizell and I had promised each other that we'd be together till the end. And now I was in the middle of breaking that promise.

'I think I'm just meant to be with you – unless you want me to go on living?' I added.

Ben considered. 'I want you to be you,' he said at last. 'Whatever you do, it's got to be your decision.'

I remembered Mizell saying the same thing. I realised that he hadn't been avoiding the subject because it made him uncomfortable, but because he was trying to give me a free choice. If I had been Mizell, I would have been crying, pleading with me to stay. But he'd just – stood back to let me decide. I felt ashamed.

The trouble was that, with people on both sides trying not to put pressure on me, I wasn't sure what I actually did want – other than everyone I loved to be alive and well and young again and in the same place.

'Uh – are you planning to reincarnate again?' I asked.

'I don't know. I might, if there's something I need to do. Only – it won't necessarily be anywhere soon in your timeline, or even on Earth. For all I know, next time I'm going to be born, a thousand years in the future, to make peace between the Druul and the Trolanni.'

'Who are they?'

'I haven't the faintest idea.'

So, even if Ben did reincarnate, we probably wouldn't see each other again. Then again, even if he reincarnated next year in my world, that was no reason why he should remember me or Firedrake, or anything of his past life. Some people believed that Ben was the reincarnation of the first Dragon Rider, Zenith, but Atticus, who had dearly loved Zenith and been driven nearly mad with grief at his death, had never even asked about it. He just concentrated on being a good friend to Ben as Ben, without needing him to be a reincarnation of his lost friend.

Later, Ben had been kidnapped by a vampire clone of Zenith who had been our enemy at first, but later became someone who seemed virtually indistinguishable from the original Zenith. Clone-Zenith and Atticus had lived together and brought up their adopted children together, and the clone seemed to think of himself as being Zenith. Perhaps he really was the long-awaited reincarnation of the Dragon-Rider, and the fact that other humans, like Ben and his friends Winston and Ivan, were also dragon-riders was to do with something different.

As I wondered about all this, a black-robed figure strode up to us across the sand, on long bony legs.

HAVE YOU MADE YOUR MINDS UP YET? he asked.

'Yes,' said Ben. 'I'm going on.'

'And I'm going back,' I said.

'Good,' said Ben. 'I love you.'

'I love you, I love you, I love you!' I said, and we hugged for a long, long time, and then turned and walked off in opposite directions.

When I woke, Mizell was crouched on the pillow next to me, and Atticus was sitting in a chair next to the bed. Mizell jumped back, startled, when he felt me moving.

'You – came back?' he said, baffled.

'We promised – together till the end,' I said.

'But – you gave yourself to a human.'

'Yes. And he gave me to myself. You see – I didn't have the spirit to run away, the way you did. I was created to be a slave, just as Nettlebrand was created to be a killer. I saw that as the whole reason for my existence. So the only way I could explain to myself why I was rebelling against Nettlebrand, was to tell myself I had decided I wanted Ben to be my master instead. He loved me so much that I came to love him, and then – ultimately, he loved me so much that I came to love myself, too, because I could see the person that I was in his eyes, and so he enabled me to be a better person than I ever thought I could. He gave me to myself – and he gave me to Mizell, too.'

Thinking back, it was only when we met Mizell that I finally started calling Ben 'Ben' instead of 'Master', and 'du' instead of 'Ihr' when we were speaking in German. He'd tried to tell me not to call him 'Master' when we were first together, and then stopped arguing about it when he realised that nagging me about it just made me feel uncomfortable. But I'd just needed longer to accept that a homunculus and a human could be friends on equal terms.

I was crying, now, but not sobbing with despair the way I would have once. If anything, I was crying with gratitude at having been allowed to know Ben. And Mizell, who was usually so tough and self-contained, was crying too, with relief at having me back.

Atticus leaned towards me. 'You're b-braver than I was,' he said shakily. 'I didn't know if you could be. I'm – I'm sorry I misjudged you.'

I wondered what he was talking about, and then I remembered. Decades ago, Atticus had suggested that if I didn't have a self-destruct mechanism to ensure that I died when Ben did, I might be so distraught with grief at his death that I would do something I would regret. The way Atticus had when his Dragon Rider, Zenith, had died.

And now, Ben's death had brought back the shock of Zenith's death all over again, and Atticus seemed to go back to being the frightened, lonely, fourteen-year-old vampire boy he had been then, sobbing with grief over Zenith's death, and sorrow over the terrible mistakes he had made. Even though Zenith had somehow come back to him in the end, it didn't wipe away his feelings of guilt. I wished I was human-sized so that I could hug Atticus. Instead, I climbed off the bed onto his knee and hugged his icy-cold hand.

'You didn't misjudge me,' I said. 'If Ben had died then, when he was sixteen, I wouldn't have coped. Or – if I had, it would have been because of you and Barnabas and everyone, and because – well, because I wasn't alone in the world the way you were. But I'm not the same person I was when Ben was sixteen, and you're not the same person you were when Zenith died.'

It was tempting to regress to being the person I had been back then: someone who would have retreated into myself, and wished there was someone to come and rescue me from my dark mood, the way Ben always used to. But I didn't need to, now. Ben had been my first friend, apart from my brothers, but he was no longer my only friend. Life was going to be sadder and lonelier, but it hadn't become meaningless because he had died.

And there was something else I realised I needed to say, quite urgently. Apart from people who have been infected with vampirism by being bitten, or who have one or more vampire parents, the people with increased risk of becoming vampires when they die are people with red hair, and people who have committed suicide. I certainly qualified on the first count, and allowing myself to love a human when I knew that this could kill me arguably counted as suicide.

'Atticus,' I said, 'can you keep an eye on me for the next few days? If I try to bite Mizell, promise you'll stop me.'