Yes, you can change the X and Y scaling for symbols very simply. When you've picked a symbol, just right-click to call up the Symbol Parameters pane as you would if you wanted to change the scaling ordinarily. There, you'll see an empty checkbox for "Independent X and Y". Click that box, and try whatever scaling seems appropriate for each axis - this is almost always trial and error, so you just need to persist. I usually find that what I thought should be the X axis is really the Y, but that's likely just me 😉...

I don't think there are any symbols that will do this for you easily, so you'll need to draw most of it. Thus you can just pick whatever style seems best to you for the look you're wanting to achieve.

As your initial drawing shows though, even a simple pit will give you a template from which to work with for this, although it may help to pick a spiked pit to assist in getting the descending pillar polygons to look right at their various angles. The wall lines alone help with those near the pit's edges, after which you simply need to adjust the angling as you work inwards. There's a spiked pit in the standard DD3 symbols, for instance. To make it rectangular, simply set different suitably-sized X and Y coordinates when you're adjusting the symbol's size. This will produce distortion (especially of the spikes), but as you're just using the symbol as a guide for drawing to, that shouldn't matter much.

The pillar polygons will need some shading applied to make it look like they're fading away into darkness (like the pit walls in your post here), which can probably be best achieved using additional polygons drawn over the "lower" parts of the pillars (try the darker Solid bitmap fills that have various transparencies built in), coupled with some edge fade effects to blend one to the next (you'll need to set up several extra sheets to get this to work well enough). It probably won't be quick or easy to do this, because you'll have to keep stopping and thinking about what to do next (I know I would, which is what I'm basing this on!).

If you get stuck, just ask again here. Or maybe someone else more technically adept will come up with a much more elegant, and swifter, solution in the interim!

We've had repeated discussions about submarine mapping styles on the Forum here. I've tinkered about with existing styles and a few additions of my own for use in the Community Atlas. I'd definitely love to see someone tackle these more fully, but am far from sure it'll happen in the short-term.

The main problems revolve around not having access to the same kind of imaging you can get easily for surface landforms, so it's much harder to create artistic symbols and fill styles, because these simply don't exist, and never have done. The Tharp style is fine, but essentially, this is all there is to draw upon of this type for the deep undersea environment especially, and it falls apart as soon as you try to use it for areas less than oceanic in scale, primarily because the detailed mapping to help also to a large extent doesn't exist (plus these maps are interpretations of instrumental readings, such as sonar, which don't give the same impression you would get if you saw the features in reality; the Tharp maps are calibrated and redrawn artistically to fit with more familiar visual landscape impressions - like using wall shadows in dungeons, say, even when you know those couldn't be really there).

There are undersea features that have no land-based equivalents, such as seamounts, trenches and mid-ocean ridges, much of which remain remarkably poorly-understood, often because the areas are difficult to access and impossible to image visually on anything beyond a very limited scale. Even trying to find a reliable drawing of what a single, fully-grown giant kelp looks like (they're usually far too big to image, at up to a couple of hundred metres in height), proved a nightmare when I tried to do so some years back for my Atlas symbols. Photo images show only bits at a time, or from oblique angles, because of the size issue, and the fact they grow in dense forests commonly makes it hard to tell which bit belongs to which kelp! It is possible to make an artistic interpretation, much as the overland styles often use slightly vague interpretations of trees, and it's that "vagueness" I relied on, certainly!

So yes, one more vote for more undersea mapping options (though I have voted for this repeatedly anyway 😁) - just don't hold your breath 😉!

Still reeling from the shock that the style wasn't called "Sinister Suers", naturally 😉!

Constructing sets of connected maps like this is always an organic process, with ideas for one influencing the other along the way. For these "Crypts" designs, I've been referring to Inkwell's own "Dungeonmorph Delves and Descriptions" book, one of which options has included an order of necromancers that collect strange things from many places, storing them in their own tombs, along with reminders of their greatest leader. Since this chimed with a very long-standing idea of my own from many years ago (it's a useful way of explaining random dungeon layouts sometimes!), I decided to indulge especially heavily from the Inkwell notes for this design, with just a few adaptations and changes, since it all seemed to flow together quite nicely otherwise. Additional elements - notably among the treasures - came from the random tables mentioned in my first posting here, or ideas that occurred along the way. Thus we arrive at The Crypt of the Necromancers map:

The mapping style is Sue's Creepy Crypts 1 & 2, from Annual issues CA 186 and CA 188, partly because I'd only used elements from it last time, and wanted to try out the complete style, partly because - of course - it's ideal for constructing burial layouts, and partly because it has those really invaluable individual step symbols, perfect for creating daises, or when the mapping design needs a non-standard staircase that rises straight before becoming a quarter-spiral at the top (in room 4 here - hopefully a little more visible on the Gallery version of this map). I've also used a couple of Sue's other symbols in this map, one from her City Domes Annual, CA 144A, the other from the CA 175 Marine Dungeon pack.

The outside, cave entry and long cavern to get to the dungeon proper, were simply sketched-in by hand - and those two blind side passages in the Cavern aren't accidental - after the Crypt layout had been drawn-in. The mechanism for drawing caves in this style is somewhat different to normal, and took a little experimentation to get right, particularly in relation to masking the outside of the Crypt's straighter wall-lines, as that's drawn a different way. And that 10-foot grid was actually drawn on three different sheets as a result of this - some of the lines only by hand!

I knew from the original sketched layout that there'd be space around the design to add a places list (expanded considerably by the text and PDF accompanying Atlas notes), and I opted to indulge further by using more of Sue's Creepy Crypt symbols as decoration to fill some of the spaces this left, and to add to the atmosphere. The coloration is deliberately muted and grey, in-keeping with the generally gloomy aura The Scar region encourages, aside from a Necromancers' Crypt not really being a likely place for bright wallpaper with cute puppies and kittens frolicking over it (though that would rather challenge an adventuring party's expectations)!

The next layout is to be from Inkwell's "Delver" dice set, which has a mixture of cavern and dungeon aspects to the designs. That's scheduled for somewhere on Kraken Island in the Forlorn Archipelago...