Tl;dr
Serin is a tiefling whose mother died of a plague when she was pregnant with her. She was tainted by the plague, as well as from being born 1 month early. This means she's sickly and has a range of health issues, not to mention corrupted magic.
Some excerpts from my description of her.
"a tiefling woman, just shy of five feet tall. Her skin is reminiscent of porcelain, with its pale white translucence, and her long ivory hair is tightly braided"
"but her gaunt hands hint at an almost emaciated frame underneath.
"two long and slightly curved white horns are revealed, along with a couple of long elven ears"
"A pair of piercing white eyes scan the docks with an exhausted expression"