Graun the Giant- An immense and towering redwood, Graun holds little time for men and for their actions. Nearly five centuries, he hasn't yet hit his middle age. Graun lives by sea and by cliff, preferring solitude to the wars his kindred make on men.
Graun spends his time reshaping the land, smashing stone and sending sees, working towards a plan for the land that the winds command. He is heedless of men, and of their anger and fear toward him. He will build and break the places of men without worry, or reason known to man. All he cares about is his work, and for nothing and no one else.
That's the thing about archetypes, they're the first and foremost things that we think of, the primordial fears and dreams. Elves are mystery and alluring, something beyond human nature and control. Dwarves are the earth, solind, ever-present, and generally benign. Orcs are our memories of the past, of days when tribal warfare was common, and of the dark side of nature.
Dragons skirt the boundary of good and evil, being either deadly or benign. Either way, they are often set as the most powerful of mortal forces, the greatest threat or aid to man, our greatest challenge.
And these archetypes have been in existence since man first learned to dream, present in every culture in some form or another. They are the tales of childhood, and the dreams we long to have again. They are that which everyone tries to find, an incarnation of imagination
I often leave ideas half finished and full of plotholes, in part to allow me to fill it in on my terms, in part to make sure that other people can fill it in as they like.
I actually based both Ram and the castle off of the books Castle Perilous, which is another reason that I don't want to add too much detail. It's fine to borrow ideas, or be inspired by a location, but if I go into too much detail, I might be tempted to make it too much like its inspiration.
A lot of the lack of detail stems from the fact, though, that I haven't really got a clue as to what the castle looks like, how Ram got where he is, and so on and so forth.
I don't play the planescape setting (I didn't even know it had a name), but I did read about the city of Sigil in one of my books.
As for culture and history for tieflings, I don't know a ton either. My style is mainly to make stuff up on the fly, so I rarely look at stuff beyond general descriptions, and pick and choose what sounds cool.
Sorry it's so lacking in detail, I know it isn't a top-knotch post like some of the ones on the site, but until I myself know more about Castle Incarnadine, I can't really expand it.