Thomas is not his real name.
In the eastern land of Tian Xia, a human family who greatly enjoyed the status afforded them by their prestigious ancestry was shocked when their firstborn child was an oni-spawn tiefling. After some discreet divinations, it was determined that the child was the manifestation of demonic heritage that had been dormant in the family's bloodline for countless generations.
While keeping the mother and child hidden at home under the pretense of being ill due to a complicated birth, the father wrestled with the prospect of losing all his social status to a tainted ancestry. Fearing he would lose everything and seeing no acceptable (in his mind) solution, he eventually resolved to kill the pit-stained child and keep the whole thing secret.
Fortunately for the young tiefling, his mother was more compassionate. Realizing her husband's intent, she fled under cover of darkness, taking her precious child with her on a desperate flight to the west. She had heard of Absalom, the City at the Center of the World, where people were diverse enough that perhaps her child would be a little less stared-at, a little less forced into constant self-defense.
And so she traveled. Sometimes walking, sometimes hitchiking, sometimes running. While her husband back home faked the death of both her and the child (thus retaining his beloved status), she trekked countless miles, sometimes staying for extended periods with generous (and open-minded) souls, sometimes sleeping on a forest floor and telling her toddler that he could go ahead and eat their only food because she wasn't hungry.
The journey was long and hard, made longer and harder by not knowing the way, or needing to recover from an illness or injury, or needing to hide from dangerously scared townsfolk. The tiefling was a teenager by the time they finally reached the Inner Sea. Unfortunately, his mother did not get to see him arrive safely at their destination. After one too many nights in the rain and too much distance between them and someone willing to house them for a while, she died unceremoniously in the wilderness. The tiefling, now nearly an adult, dug her a grave and mourned alone.
Or so he thought.
The goddess Iomedae had plans for him, and sent a startling vision to a devout paladin in Absalom: the paladin was to venture alone into the wilderness, encounter a tiefling, and bring him back with her to Absalom to be trained as a cleric! Despite warnings from her peers that this could be trickery of a demon, she followed the prompting of her vision and, upon reaching the appointed place, found not a snarling villain but a mourning teen in the process of placing a lovingly-crafted marker atop a fresh grave.
Moved by what she saw, she greeted the tiefling warmly - more warmly than anyone but his mother had ever treated him. Realizing that he could trust her (and that he had no choice, as a half-starved commoner is no match for a well-equipped paladin), he went with her back to Absalom to learn of Iomedae and the future he could have in her service.
Almost ten years later, the oni-spawn is starting to become known both inside and outside the church of Iomedae. Having assumed the name Thomas to shield his family (mostly his mother's memory) from shame, he now travels the Inner Sea as both a Pathfinder and an agent of Ollysta Zadrian's Silver Crusade. With the wisdom to differentiate between the evil and the desperate, and the strength to cut down the former and protect the latter; Thomas the Tiefling Hero spreads the holy light of Iomedae wherever he goes.
Thomas is strong and noble, willing even to throw himself in front of a blade aimed at his allies. Ever vigilant and always prepared, he strikes down evil with his goddess' favored weapon, using magic both to bolster his combat ability and to negate whatever tactics his enemies might use to confound him and his allies.
Though his life has never been easy, Thomas' biggest challenge is yet to come. There are murmurs of late; murmurs of trouble at the Worldwound. Though Thomas has faced a few demons in his career (even venturing once into hell on a rescue mission), the time is coming when he will be called upon to march against the mustered hordes at the worldwound. The danger will be great, but so is Thomas' courage and his faith that Iomedae will be guiding both his spells and his sword arm.
UPDATE: It has begun. The wardstones are failing, and forces are mustering for the Fifth Mendevian Crusade in an effort to hold at bay the surge of demons from which the wardstones no longer protect the Inner Sea. Though Thomas has not yet travelled to Mendev to engage the threat directly, he was influential in swaying Absalom's movers and shakers toward approving a bill to send soldiers to the Worldwound. Though the light of Iomedae shone through him, Thomas won't know for some time whether his work was sufficient. In the meantime, he's scheduled for a mission to recruit a troop of famous elven demon-hunters to the cause.
UPDATE: Despite a certain level of non-cooperation from their superiors, Thomas has helped secure the aid of a troop of elves. The only squad that the woman in charge was willing to spare was one that she had already left for dead in the Tanglebriar; disgusted with this callous abandonment, Thomas and a team of Pathfinders entered the demonic swamp and rescued every last elf from its darkest corners. But a single squadron of rangers won't end the Fifth Mendevian Crusade. Soon, Thomas will be embarking on a similar mission to enlist the help of the Riftwardens, though it will require venturing into Rahadoum, where everything about him is illegal.
UPDATE: By the blessing of the Inheritor, Thomas has ventured into and out of Rahadoum without being confronted by the Pure Legion. Sadly, the contingent of Riftwardens he was sent to retrieve had been captured and were being tortured by the Blackfire Adepts, making the mission a bit more complicated. Even so, Thomas helped his team ensure that every single Riftwarden was rescued as well as that every single Blackfire Adept (and their infernal accomplices) were killed. Thomas' efforts are continuing to procure allies against the demonic hordes of the Worldwound, but will they be enough?
UPDATE: Thomas has struck another mighty blow against the hordes of the Abyss. Near the Worldwound rests the tower of the late Ghalcor, fellow cleric of Iomedae. Within Ghalcor's tower resides a century-old weapon to which the Mendevian crusaders now have access. Though the cost was great, Thomas helped to secure the tower and its weapon for use against the demon armies. There may be hope in this war yet.
UPDATE: All-out war broke out in Nerosyan, as a Pathfinder meeting to which Thomas was an attendee was interrupted by a massive demon incursion. Working together with dozens of other Pathfinders and countless crusaders, Thomas helped to repel the invasion and rout the demons, slaying multiple figureheads of the abyssal army in the process. Thomas carries the will of the Inheritor with him, and those who would oppose his patron will not easily prevail.
UPDATE: Although sometimes Thomas would prefer to focus all his attention on crusading against the demons of the Worldwound, he also has loyalties to the Pathfinder Society, and the Society's goal is to gain access to Jormurdun. As such, Thomas recently aided a diplomatic expedition to secure a potential future base of operations in the Realm of the Mammoth Lords. With the help of his comrades and his goddess, Thomas has befriended a powerful barbarian tribe who will not only allow the presence of the Society but may also come to arms when the latest crusade against the Worldwound comes to its inevitable peak.