Favoured Apparel
Some apparel can be used to create an effect of an actual biological addition to your dragon, and a few of those are particularly perfect for Copper Cave Dragons. For instance, all varieties of Deepsea Bulb are perfect for these cave dragons; the Deepsea Bulb, glowing with its own light, dangles above your dragon's face and makes a perfect hunting lure, whether they're fishing or drawing in other small cave-dwelling creatures. (Any animals attracted to the glowing bulb will end up conveniently right in front of your dragon's mouth, like self-serving hors d'oeuvres!)
Roundhorns come in some beautifully coordinating colors, and work great with the subspecies lore; dragons could use these tough horns to batter away at stone while excavating their caves.
Glowing Claw Tips, brewable at Baldwin's, are also a great additional touch for any Copper Cave Dragon, whether you imagine them as a permanent biological addition or a left-over bit of glowing paint for your resident cave artist. The various types of mushroom colony, also available for brewing at Baldwin's, are a great touch for dragons who farm mushrooms, or who simply live in extremely damp cave systems, perhaps as sit-and-wait predators.
Favoured Familiars
The familiars that prove to be the best companions for cave-dwelling dragons are those already adapted to the environment, like Cave Jewels, Dwarf Truffles, Skinks, and other denizens of the Forgotten Caves. These dragons are usually particularly attracted to familiars who have similar coloration to their own, like the Emerald Cave Jewel, and ones that also exhibit bio-luminescence, like the Murktooth Bramblekeep.
They don't tend to keep any familiars that have trouble adapting to a life of damp, darkness, and stone, though they will often keep aquatic species when the clan has access to cave river or lake systems, or adequate underground pools or mineral springs. Some cave systems even open into larger sea-caves, where dragons can keep really large aquatic animals as familiars. They usually have no particular affinity for Stone Borers, but will try to acquire these mechanical golems because they're very helpful for the excavations involved in expanding their caves.
A Molten Wartoad is also a particularly coveted companion for any Copper Cave Dragon clan, as the Molten Wartoad's naturally high temperature helps to heat the nursery caves where these dragons keep their eggs, and the Wartoad's diet of stone also helps keep the caves clean when the dragons are excavating new areas; the stone waste won't have to be removed, simply fed to the Molten Wartoad. These are just a few of the familiars that Copper Cave Dragons may favor most.
Favoured Items
A Copper Cave Dragon's favorite items are a highly personal choice, but as a subspecies they are generally attracted to anything that glows in the dark. Most also live in cave systems with heavy mineral deposits, so they also tend to have an affinity for crystals and gems, and other reflective and refractive items that help amplify their own glow. Some Copper Cave Dragons have even set up elaborate systems of reflection and glowing items, by which they can light entire rooms simply by walking in, as their own glow bounces off of various surfaces they've set up, until the whole place is lit up like daylight. Their excavations often uncover riches beyond imagining in gems and ores, but Copper Cave Dragons tend not to value those items much beyond their sparkle or their value in trade with clans living above ground.
Many cave dragons love to decorate -- both their caves and themselves. They're masters of making their own glow in the dark pigments and dyes using materials like slimes and Cerdae Sparkle, and they love to decorate their lairs with claw-drawn murals, especially ones that glow. Some clans will cover their cave walls in glowing paint to brighten up entire rooms; others will mark their tunnels with glowing stripes like a map to help clan members and visitors find their way through the maze of tunnels in extensive cave systems. They'll also decorate with items like Potted Deepmine Fungi and Dwarf Truffle Spores, which they'll cultivate in little nooks and cracks in their cave walls, or in vast underground greenhouse caves, growing mushrooms and other cave-dwelling plants to snack on.
These are just a few of the items that may be found collected in a Copper Cave Dragon's hoard: