So he did.

Tyland Lannister is a second son in a story about second sons. Whether his feelings on this are as strong as Aemond's or Daemon's, we never know for sure in the books, but it's obvious that he's subservient to a mirror image of himself who only has more authority because of a few seconds separation between twins. It's a great display of both the arbitrariness and rigidity of succession.

His initial role in the Dance is as the master of coin for the greens. He's depicted as a typical Lannister: charming, comely, and cunning. He did what any savvy accountant would do and divided the crown's treasury amongst different allied regions for safe-keeping, ensuring that if King's Landing were sacked, their enemies wouldn't loot their coffers dry and they'd still have plenty of gold for their war efforts.

And of course, King's Landing gets sacked. Tyland is put in the black cells and ordered to be tortured by Rhaenyra to extract the gold's whereabouts. Winter is coming, people are starving and rioting, her army is dwindling, so she desperately needs that gold. Tyland is gelded, maimed, disfigured, and blinded but the torturers get nothing out of him.

Mind you, this man has been a rich, pampered bureaucrat all his life and he endured all that without breaking. When Aegon II releases Tyland from those cells, he has no fingernails, his eyes have been gouged out and/or sewn shut, this man who was once known for his good looks doesn't look human anymore — but he still manages to maintain his wits so much so that he plays an important role after the Dance.

Even with Rhaenyra dead, there are still armies raising their banners for her eldest surviving son, Aegon Trois. Tyland tells Adult Aegon to kill Child Aegon because obviously, the latter threatens the former's claim and Tyland's understandably angry over what his mom did. Aegon Dos is like, nah, I'll keep the boy hostage instead — that'll keep the armies at bay more than outright killing him.

So Tyland volunteers to go to Myr to hire sellswords for Aegon 2 since their armies are pretty much kaput after six years of this civil war. Tyland is blind at this point I remind you — there is a huge chance this man will never get to go home again. But he does it anyway, because even after years of fighting, he keeps his unwavering loyalty to the monarch he declared for.

Aegon II dies while Tyland is in Myr, and Tyland goes back to Westeros just in time to see Cregan Stark use his powers as the new Hand to marry Aegon III and Princess Jaehaera to unite the green and black sides. Cregan dusts off his hands, says my work here is done, warns the boy king not to trust anyone, then leaves for the North for everyone else to sort this mess out.

Now comes the part where Tyland shines as a character. He becomes the Hand of Aegon III and when you see his policies detailed in the book, it's clear that his goal is focused on repairs and renumerations. After what happened to him, he has every right to be spiteful and bitter against the blacks, but instead he "claimed a curious failure of memory, insisting that he could not recall who had been black and who had been green." He abolished the heavy taxes imposed on the smallfolk, sent out gold to lords whose holdings had been devastated during war, and set out to rebuild the Realm's granaries and fleet. Cleaning up is a tedious, unglamorous job — and because of his monstrous appearance and former allegiances, Tyland was looked upon with distrust.

And yet, while other regents grasped for power and tried taking advantage of the 13-year-old King Aegon III, Tyland seemed to be different. If he wanted power he could have married his twin brother's widow and convinced the boy-king to route more resources towards Casterly Rock and the Westerlands. But he didn't.

Instead, he genuinely seemed to be a father figure to Aegon III.

Tyland Lannister, blind and crippled, had always treated the king with deference, speaking to him gently, seeking to guide rather than command.

And for that, many lords saw him as a weak Hand. But Aegon, who cared for very little and never laughed and was always sullen, seemed to care for Tyland.

When the plague ravaged King's Landing, Tyland dutifully prioritized it over quashing the Ironborn raids at Lannisport. He was the last person to become afflicted with the Winter Fever, and the king sat by his Hand's side during his final hours. When the council starts discussing who should be the new Hand, Aegon (the boy who rarely ever speaks) says:

I would have Lord Rowan as my Hand. Ser Tyland thought well enough of him to offer him my sister’s hand in marriage, so I know he can be trusted.

This boy trusted Tyland, the man who only years ago wanted him dead.

So it's easy to imagine that this man saw Aegon III as the boy he was responsible for, as the son he could never have because of what the war had done to him. Tyland Lannister was a broken man who despite losing everything, his king and his brother and himself, kept a broken Realm and broken boy together when everyone else swarmed like vultures just trying to pick at carcasses.

What motivated this man's loyalty for a boy whose mother mutilated him? Did he regret pushing for the death of an innocent child and this was his penance? Did this man who gave everything for his cause think that this boy was something that could still give all that sacrifice and tragedy meaning? Was the mercy and kindness he afforded an apology for the horrifying trauma that scarred this boy — did he feel responsible for his mother's downfall and the failure to save his uncle? Did his disfigurement and blindness allow him to let go of the man he once was and become someone capable of seeing the folly of pride and power?

Here is his obituary in Fire and Blood:

Ser Tyland Lannister had never been beloved. After the death of Queen Rhaenyra, he had urged Aegon II to put her son Aegon to death as well, and certain blacks hated him for that. Yet after the death of Aegon II, he had remained to serve Aegon III, and certain greens hated him for that. Coming second from his mother’s womb, a few heartbeats after his twin brother, Jason, had denied him the glory of lordship and the gold of Casterly Rock, leaving him to make his own place in the world. Ser Tyland never married nor fathered children, so there were few to mourn him when he was carried off. The veil he wore to conceal his disfigured face gave rise to the tale that the visage underneath was monstrous and evil. Some called him craven for keeping Westeros out of the Daughters’ War and doing so little to curb the Greyjoys in the west. By moving three-quarters of the Crown’s gold from King’s Landing whilst Aegon II’s master of coin, Tyland Lannister had sown the seeds of Queen Rhaenyra’s downfall, a stroke of cunning that would in the end cost him his eyes, ears, and health, and cost the queen her throne and her very life. Yet it must be said that he served Rhaenyra’s son well and faithfully as Hand.

Tyland wasn't extraordinarily badass, noble, or even skilled. He was an excellent politician but no way the best. But I think that's what makes him compelling to me — that he's this down-to-earth depiction of a POW, a war veteran by all accounts, trying to pick up the pieces and slowly glue what remains of the Realm and himself back into something vaguely human.