Arda and Theme
Arda, which is the land before we see the lands of Middle Earth in the second and Third Age, is a world of the First Age and the most interesting of all three ages and of any land ever conceived in the canon. Several ideas present themselves to me regarding Arda, the first of which is the most intriguing - the creative aspect of the land. Things need to be built, all around. We start off with almost nothing but an idea.
To conceive of such lands would by first principle mean resolving fundamental forces of life, death, evil, good all in abstract form. And bringing a coherent narrative to them involves capturing not only the tales themselves, and the Silmarillion, but the themes behind them as well. It is something one cannot do in the abstract, and will require all of one's focus and strength. And it does not necessarily preclude the human conventions and relationships that would arise from such effort and within or even without such community. (The tyrant's face is red)
And what a war that must be fought, in ourselves and in other worlds - to succeed. The themes that were established both before the canon of Tolkien's work - the basis of his stories and the strong coherence that was established throughout - are a challenge, and also if you look carefully enough, given again, this only chance - truly. A blessing in disguise. [mortals never know]
nothing quite like being the lord of evil to keep you out of trouble.