Terrence Higgs was born April 29, 1978, to the aging Higgs' couple, known in Magical Law Enforcement for their tendency toward brutality. He was quick to defy them, displaying his first bit of magic at the age of four by setting his father's hair on fire. Not long after, his mother became pregnant again, instilling in Terrence a completely rational fear of violent pregnant women. When his little sister Amelia was born, Terrence took her under his wing as quickly as he could, becoming an unconventional combination of an older brother and father figure. Amelia was the main reason why he bothered attending etiquette and ballroom dancing lessons and learned to play chess. She also gave him the nickname "T", since she found his name difficult to pronounce, and it stuck. He looked after her until he went away to school at the age of 16, which was very difficult for the both of them.
After a few years of pranking and wreaking havoc on his own, Terrence took on a protege in Zacharias Smith, soon to be dubbed "Z". Although Terrence did well in his classes - expecting nothing less than perfection from himself, even in subjects he considered irrelevant - and played Quidditch, he made no other close friends until the arrival of Ella Lestrange, almost exactly one year before he was to graduate. However, he did get around a bit with the female students, including Morag MacDougal and Pansy Parkinson. Later, he nearly shagged - and then befriended - Tracey Davis, who then began dating Zach.
Terrence entered Age of Darkness in his last few months at the Slytherin Academy, and was determined to make the best of them. He'd already had quite a track record, of course - quite a bit of mischief, excellent marks, tutoring his protege, and playing Seeker for the Aranaes, captained by Ella Lestrange (to date, the only authority figure Terrence has ever taken an order from completely willingly).
He began his last few months with a new project - to break in the most rowdy servant in the castle, one Anthony Goldstein. He knew beforehand that the servant enjoyed - or at least claimed to enjoy - painful torture, and thus tried a new method: Chinese water torture. It failed, however, and he was unable to make a second attempt. Rather than return to his service, Anthony painted an enormous prick on the staircase of Slytherin Academy, getting himself put into isolation by Headmistress Umbridge. Instead of blaming Anthony, Terrence took his revenge on Umbridge with a series of pranks, including charming her cat portraits to look like male genitalia with Tracey. His favorite, however, took revenge on two birds with one Love Potion: he slipped Amortentia into Professor Umbridge's drink, designed to turn her affections toward groundskeeper Bill Weasley, who had been shacking up with etiquette professor and veela Fleur Delacour.
Fleur had incurred Terrence's wrath not long after her arrival at the Academy by messing with his head using her veela thrall, at one point causing him to crash into the stands during a Quidditch match and allow the other Seeker to catch the Snitch, losing them the game. As a result of his impertinence - for Terrence has never been known to keep his dislike for anyone a secret - he was also forced to be Fleur's dancing partner during the lessons preceding the debutante ball, which he considered pure torture. However, the Quidditch incident was the worst, since it resulted in a verbal fight with Ella, wherein Terrence was briefly booted off the team until he apologized later that night. The following day, Ella's sister Vera informed him that the fight had largely been due to Ella's jealousy over his attraction to their veela professor.
Contrary to his interactions with Fleur, which involved physical attraction and nothing else, Terrence's attraction to Ella was largely due to her wicked mind and loose cannon personality, which only amplified his own chaotic leanings. However, due to the age difference between them, he had kept their relationship as platonic as possible, up until their winning Quidditch match. In a fit of adrenaline-fueled madness after catching the Snitch, Terrence kissed Ella for the first time, in front of both of their families. Neither Bellatrix Lestrange, Ella's mother, nor his sister Amelia (who had only just arrived at the school) were particularly pleased about this.
In canon, Terrence would have graduated the year after Umbridge's reign to become an Unspeakable. His lover and lifetime partner in crime, Ella Lestrange, would have been Ella MacFusty, from the dragonkeeping Scottish family in the Hebridean Islands.