I'm not entirely sure if the Domain I came up with fits the criteria. Technically it does describe a physical process, so it's not metaphysical, but the applications may be a bit odd. Feel free to yell at me if there's anything that needs changing.
Name & Title: Eryian, Lord of Decay.
Gender: Male.
Bio: Eryian is the second son of the God of Entropy and the Goddess of Nature. The first son, his elder brother, was born with the Domain of Corrosion, the power to erode away nonliving objects and forces, whereas Eryian inherited the Domain of Rot, which allowed him to decompose the living. Despite their kinship, the brothers' personalities were completely different; the elder was aloof and indifferent, believing only in his own pride, and his inherent right to rule over those he deemed lesser than himself. The younger was gentle and carefree, for although his Domain had taught him the transience of all mortal beings, that knowledge only led him to treasure life all the more.
In time, the day arrived when the gods vanished, and the Enlentai found themselves without guidance. Eryian's brother, freed from his former responsibilities, departed the former dwelling place of the gods, intent upon establishing his own dominance over the mortal races. Unable to ignore his elder sibling, Eryian pursued him, eventually catching up to him in an isolated vale. There, the two brothers argued, the older calmly explaining why his birthright included the wisdom to guide lesser beings upon the proper path, the younger stubbornly insisting that they deserved the chance to forge their own way. As the dispute grew increasingly vehement, neither side willing to accept the other's assertions, Eryian's brother became more and more callous. Finally, at the height of the argument, he drew an ensorcelled dagger, bringing it plunging down toward his younger sibling's chest. Unprepared for the sudden attack, Eryian panicked, recoiling and trying vainly to ward off the weapon. At that moment, his fingertips happened to brush against his brother's arm, and his ordinarily suppressed powers unleashed themselves. By the time Eryian regained control of himself, it was too late; he could only watch in blank shock as his brother's flesh slowly rotted off his bones.
In time, Eryian returned to the land of the Enlentai, telling no-one of what had transpired in the lonely vale. Those who knew him noted that he seemed sadder, somehow, and less carefree, his former innocence tempered by an expression of profound regret. Moreover, he also began avoiding physical proximity with others, as though he were somehow afraid of touching them. Shortly after his return, Eryian learned of an individual calling himself the Ice King, who sought to establish himself as the sole god. Somewhat reluctantly, he decided to join the other Enlentai in their mission to stop Sicilis, seeking primarily to atone for his elder brother's demise.
Eryian is the Lord of Decay, having inherited the Domain of Rot from his parents and unintentionally conquered the Domain of Corrosion formerly controlled by his brother. Together, they form the Domain of Decay, which allows Eryian to deteriorate both living and nonliving objects and forces in an area around himself. His Domain strengthens in proportion to proximity; a thrown rock a meter away from him might simply suffer a decrease in velocity as its momentum decayed, whereas a rock an inch away from Eryian's skin would very likely erode into dust before reaching him. However, he cannot cause other living beings to decay unless he remains in tactile contact with them, and must consciously will his powers in order to do so. Due to Eryian's own reluctance to hurt others, he finds it extremely difficult to utilize his Domain to inflict harm, particularly given the gruesome nature of the suffering it creates.
Despite his possession of a rather macabre Domain, Eryian is a fundamentally compassionate individual. He typically displays a serene, cheerful demeanor, and tries to seek peaceful resolutions to conflicts wherever possible. The youthful impression that he gives off is more akin to that of a mortal than an Enlentai, although his mannerisms are occasionally tinged by moments of deep sorrow. Although he knows that Sicilis's actions are inexcusable, Eryian secretly hopes to reason with the Ice King, and to turn the latter away from the path of ambition, as he could not with his own brother.