World of Astra
Tieflings (PHB, p48) are moody, darkly colored creatures, with strange horns, tails, and flinty, obsidian eyes. They are known to have natural control over magic, and are particularly connected the Crimson Wind. to creatures that come from the far side of the Gates of Metalia, strangly locked portals that are said to lead to a dark, forbidding mirror of Astra. Originally warriors that the spilled out in a great hoard from those gates, they were eventually beaten during the epic final battle over the Seytalis Gate. Locked onto this side of the portals, many tieflings, among other creatures from that hoard, were forced to create a new future for themselves. While many tieflings have grown to accept and even enjoy this life, others still wish to return to thier homelands. This has lead to a common philosophy or even religion for some tieflings, known as the Key of the Awakening.
While all adherents to the Key of Awakening wish to return to their ancestrial lands, there are two primary camps as the the best way to achive this. The first belive that the problem lies within, that they will not be accepted until they learn the lessons that Astra has to teach them. They belive that by intense meditation and physical conditioning one can achive a state of spiritual bliss, allowing one to simply pass through the Gates, and move to the other side. They are commonly find adventuring a test, in order to pratice and prefect thier bodies and minds. The other camp belives that the problem is that the Gates themselves are locked by some force, and the key hidden from the world. They delve into deep caverns, practice esoteric spells, and attempt communion with the gods. Their focus is on the search, hoping that some clue or secret might help them find the key to opening the gates.