Infernal Architecture Stuff

In regards to the castle, it really could go quite a few ways. For architecture, it varies depending on the time period and the infernal. In general, they make everything big (partly due to large demons being commonplace) - for an infernal, a single story is probably closer to 5m, simply because of the presence of Kashlovians and Bausfrahr, who are some of the largest demons and common in courts (stories can be taller - Araunth's palace would probably have stories closer to 15m, as the demon himself is 10m tall). Height is also important for defensive applications - a 10m high wall can literally be jumped over by many demons, so anything less than 20m is probably laughable in their eyes and they'll definitely go higher if they can, including terraced walls. They also tend to favor strong materials rather than pretty, although strength will include magical enchantment capability and thermal resistance/capacity.

From there, architecture varies a bit by infernal. Demons favor massive displays of raw material - lots of granite, black stone/steel (which are in-setting varieties with innate magical properties that make them nearly impossible to cut or process without magic), marble, sandstone. They also tend to just throw a whole lot together and see how it comes out - you're more likely to get a Notre Dame than anything the Romans built, for instance. French Gothic is right up their alley, in terms of both size, design and materials. Devils probably vary a bit, depending on what they're trying to invoke. They're also more likely to try to reproduce scientific approaches to architecture, so lots of Roman, Italian, Venetian and even Persian or Byzantine influences. My vision of Ruathym (Malificent's capital in the Empire) is of the Persian city from Two Thrones with that massive spire-like city, but with a sprawling Venetian city full of canals, back-streets etc away from the 'upper class' parts of the city. Ariel preferred ancient Greek architecture, as that's what the Empire used long ago. Nowadays, Ariel's cities in Hell probably look like something out of the early 19th century (hence why Tyrisa is in a suit) with some Victorian elements whereas Malificent is probably copying Ahm with some edges - with massive spires of stone that would be hundreds of metres tall, bridges connecting them in the air, with plazas between them, and entire defensive bastions built around their bases, with all the living quarters, markets etc for the commoners in them and underground. So yeah, architecture can vary tons but should be absurdly overstated, even compared to AEQ levels. If the infernals built Shropham, it would have been three platforms (rather than one) sitting atop the lower city, with massive defensive towers around the edges that would spew out massive blasts of hellfire from half a kilometre in the air or higher.