Yes, but it is one word, The Doomstar, and in the case of Gormegast is is on a large moon/dwarf planet about the same size as Pluto in your star system.
However, the volcano is huge, and there is no audience chamber in it, rather it is the propulsion device. Because of its size, it looks like one of Robert Heinlein’s [url=https://www.google.com/search?q=heinlein+torchship&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjxrJXamdHRAhXK5IMKHdYtCaMQ_AUICSgC&biw=1280&bih=707]torchships[/url], only made out of rocks.
When fully powered with elemental portals, it moves very much like a torchship as well. It is heavily armed and has shields. And of course, an aethereal drive for FTL travel.
At last contact it was orbiting a large gas giant.