Doran Martell rules Dorne from a chair he can barely walk to unaided, gout having claimed the use of his legs well before his most important plans came to fruit, and that visible frailty is, by the account this encyclopedia finds most persuasive, at least partly performance. His sister Elia Martell was killed during the Sack of King's Landing in 283 AC, along with her children by Rhaegar Targaryen, on Tywin Lannister's order and by Gregor Clegane's hand — and Doran has spent every year since arranging a reckoning for it slowly enough that almost nobody, including most of his own family, has believed he intends one at all.
That patience has cost him openly. His son Quentyn was sent to Essos to press a marriage claim on Daenerys Targaryen and died there attempting to prove himself worthy of a dragon's back — burned, not ridden, in Meereen. His daughter and heir, Arianne, spent years convinced her father favored her brother over her and plotted around his back rather than with him, a misunderstanding Doran allowed to fester rather than risk the secret it was protecting.
What that secret amounts to — how deep Dorne's hand runs in the conspiracy returning a claimant styled Aegon Targaryen to Westeros with the Golden Company at his back, and how far Doran is willing to go now that the waiting is over — is still unfolding faster than the Citadel's records can keep pace with. What is not in doubt is the debt he has been keeping since 283 AC, or his intention, however long deferred, to collect it in full.