‘Where did this unforeseen enemy come from?’ That’s the central question in this third novel of the Aldabreshin Compass quartet. Swiftly followed by ‘how did they get here?’, ‘why did they come?’ and ‘why are they so brutal?’

Kheda and his allies, old and new, discover most of the answers as Western Shore unfolds but before I could write any of that, I had to work out all these things for myself. Not only deciding where these unknown invaders did come from but establishing what had changed to enable them to cross the vast western ocean, since they’d never been seen before. ‘Well, they just decided to,’ simply wasn’t an option, any more than ‘because they’re just evil,’ is ever a satisfactory answer to ‘what makes the bad guys so bad?’

At least I had a map of the Archipelago to start with. I’d learned my lesson after having to reverse engineer the original Einarinn map from accurately calculated travel details in the text and my (literally) back-of-an-envelope sketch not long before The Thief’s Gamble was published. Okay, my husband had to do the actual work – I was and remain thankful that he’s an engineer whose apprenticeship including training as a draughtsman. Incidentally, he’s the one who insisted the Einarinn maps have projection lines, when I explained I needed a map which I could put a ruler on anywhere to measure distances on the same scale. He naturally felt thoroughly vindicated when we got an enthusiastically appreciative letter from a Geography Ph.D student in Washington State, USA, for whom flat-earth fantasy maps were a personal bug bear. But I digress.

As you see from this far more extensive map, I had the upper half of the Archipelago mapped by the end of The Tales of Einarinn, so extending the island groups and chains southward was easy enough. But then I had to decide what lay out to the west. ‘Here be dragons’ might be literally true but I needed to know where and why, and crucially, why they were on the move for the first time in more than living memory.

Because ocean and atmospheric currents had changed somehow? That looked like a promising possibility so I went off to do some research, including but by no means limited to buying The National Geographic Atlas of the Oceans and doing detailed searches through my National Geographic Archive CD-Roms. I learned all sorts of useful facts about jet streams, thermohaline circulation, deep cold water flows, tectonic plates and undersea ridges, as well as weather patterns, and what causes trade winds, the doldrums and El Nino. All fascinating and all terms and systems it would be impossible to reference directly in an epic fantasy novel without ruining, well, the atmosphere. This is definitely a situation where the Iceberg Rule of Research applied. Only a tenth of this work shows above the surface, which is to say, appears in the final novel, but that couldn’t be there without the other ninety percent.

Now I had the key information which I could add to my map and integrate into the story. More than that, I was now seeing more ways in which wind and sea currents and the distribution of islands would affect travel and alliances within the Archipelago. This work was already influencing the course of the events I had planned for Eastern Tide. It ultimately contributed to The Hadrumal Crisis as well but that’s another story.

But all this work stayed on the papers on my desk. When the Aldabreshin Compass was published in paperback in the UK, we were all forced to agree that the scale and layout of the Archipelago meant reproducing the whole thing at that page size could only offer readers a scatter of uninformative dots. When Tor produced the US hardback, they had more room to work with and included a very handsome map but that could still only offer a section of the Archipelago, unable to show its relationship to the mainland.

So only a limited number of fans got to see even that much. And as with the admirable Einarinn maps in the Orbit paperbacks, the copyright for that specific depiction of my original material remains with the publisher, not with me.

Well, that was then and this is now. As those who’ve bought Southern Fire and Northern Storm already know, these new ebook editions include a map of the entire Archipelago and now I’m adding it to the website. This time I have my elder son to thank, who took on the not inconsiderable task of cleaning up the digital scan of my master paper copy, with all its creases and pencil scribbles, as well as collating all the other bits of information jotted on sections I’d enlarged and printed off separately to cover with more coloured arrows and notes. Finally he added his own bit of artistic flair, deciding it needed to look like something found in a Hadrumal wizard’s archive, maybe left by some ambitious cloud mage seeing just how far up he could take a scrying spell. I reckoned he’d earned the right to do that.

So is this it? Well, as you can see, there’s still an awful lot of this world still to be mapped – and we haven’t even found out what might be happening in those lands we can already see but haven’t yet visited…