gold
鏐 centers on gold as a precious metal, specifically referring to fine or pure gold.
鏐 combines 金 (metal, gold) with 翏, which likely contributes the sound. The exact historical development of 翏 is uncertain, but the character as a whole denotes a type of fine gold.
The left side is 金 (gold), and the right side 翏 looks like feathers (羽) with extra strokes, suggesting something light and pure. Imagine gold so fine it feels as light as feathers.
For リュウ, picture a gold dragon (竜, りゅう) guarding a treasure of fine gold: 竜 -> リュウ, and the gold is as precious as the dragon itself.