The plane of Tartarus, not unlike Ylembica, have seen their fair share of war, whether it be with Angels, Demons, or their own kind. Devils, unlike Demons however, follow rigid political systems, with a strict caste that pushes the weak down and forges strong leaders of Tartarus. Not all that reside in Tartarus abide by, like, or even tolerate the caste into which they were subjected, there has been more than one rebellion against the supreme lord Asmodeus. Tartarian Titans have fallen, killed one another, risen and fallen in their ranks, and otherwise reshaped the structure of the Tartarus. One thing has remained constant throughout every revolution, every reshaping, and every layer, the suffering. There isn’t a spot in any seven layers of Tartarus that isn’t defined by pain, misery, deceit, and anguish. Devils were able to withstand Tenno’s absence with very little change because they gain there power from the suffering of the mortal races.
Devils derive their powers through the power that oaths, contracts and pacts hold, specifically the power the gain from the denial of one’s free will, or their destiny. As such, Devils act as the executors of contracts, from small to large, though the large ones get forgotten about much more often. A contract for 10 gold holds much less weight than one for the disputed land between nations. While a Titan might not bother themselves with the execution of a family squabble, an imp or lesser devil might act to execute the contract and possibly punish those in breach to gain what to them is a great amount of power.