—Darin in Chapter E19/H20
Lord Darin was well known by the people of Laus for his uneasiness to Ostia, always claiming that Laus should be the strongest of the Lycian territories. However, under the influence of Ephidel, a servant of Nergal, and the Black Fang, Darin began preparing his territory for full-scale rebellion against Ostia. Unknown to him or the Laus soldiers, this was actually a well-conceived plot by Nergal to cause a war within Lycia that would generate enough quintessence for Nergal to open the Dragon's Gate.
His plans were deterred by Marquess Pherae, Lord Elbert, and Marquess Santaruz, Lord Helman. Elbert was brought to the Dragon's Gate to be sacrificed because of his strong quintessence, and Helman was quickly disposed of by Ephidel, but not before pointing Lords Eliwood and Hector to Laus.
With the two lords coming to investigate the disappearance of Marquess Pherae, Darin sends his son, the cavalier Erik, to dispose of the two lords and their companions with aid from the Laus cavalry. However, Eliwood, Hector, and their companions prove too strong with the aid of Mark, Erk, and Priscilla, and the Laus cavalry are beaten back. With the forces dwindling, Darin, persuaded by Ephidel, leaves the remainder of Erik's forces to Eliwood's and Hector's forces and flees. After the battle, Erik tells the lords everything he knows.For the moment, Eliwood is in denial that his father would be involved in a plot to overthrow Ostia, as Erik claims. Erik is then presumably left in Laus Castle, although it is unknown where he was when Sealen and his forces invaded the castle in Hector's Story.
Out of desperation and with nowhere else to go, Darin and the rest of the Laus Army captures the territory Caelin as well as its marquess, Lord Hausen, but Lyn and her vassals, Kent, Sain, Wil, and Florina, escape the siege of the castle. The three lords are reunited at the base of the castle and best the Knight Bauker. With his plot nearly unraveled and cornered in Caelin's fortress, Darin secretly departs from Caelin with Ephidel, leaving the remainder of Laus's army to be decimated by the lords' forces. Bernard, the Knight Commander of Laus, is killed by the lords in his trust that Darin will come and help, leading up to the disbandment of most of Laus's armed forces, until when they later side with Bern in Fire Emblem: The Binding Blade.
Darin, however, was not safe from the curiosity of Eliwood, searching desperately for his father. Aided by inforation from the Ostian spy, Leila, the company arrives on Valor, The Dread Isle, despite the Black Fang's best efforts to deter them. Uhai, one of the strongest Black Fang members, is noted to have died trying to delay the three lords. With his objective nearing completion, Darin holds the forward defenses of the Dragon's Gate, defending the throne. He underestimated the three lords, however, and was killed in the aftermath of the siege of the Dragon's Gate.
Darin reappears as a morph in the second battle at the Dragon's Gate, resurrected by Nergal and wielding the Rex Hasta. He is defeated in the battle, and is seen smiling as he dies a second time, apparently finding peace. His son, Erik, would join him in death 2 1/2 decades later, fighting Roy's army under Narcian's orders, with help from the Sacae-Bernese myrmidon Rutger, who joins the Pheraen forces when Clarine speaks to him.
Darin is noted by the citizens of Laus and by his son, Erik, to have been a bit arrogant, always claiming that Laus should be the strongest of the Lycia territories, but always kept a cool head and never dared speak, much less conspire open rebellion. Unfortunately, that weakness was preyed on by Ephidel and he was manipulated, becoming a cold, heartless, and power-hungry noble, claiming himself the new leader of the world. His arrogance also seems to delude his common sense as he falls prey to Ephidel's schemes, claiming that Nergal can control powerful dragons.
He also seems to be quite stubborn, as he refuses to let Priscilla leave Laus until she agrees to marry him. He is also noted by the villagers in Laus to have been behaving quite strangely during the events of The Blazing Blade.
However he did have a soft side, particularly towards his son Erik.
During the chapter Dragon's Gate, Darin has high HP and defense/resistance ratings and a speed rating notably superior to those of the previous armored bosses , but a well-trained axe user can bring him down quickly. Using Hector and his personal Wolf Beil is the most recommended. Otherwise, if Oswin is promoted and has a D rank in axes, have him use a Hammer. If Hector has developed a support with Eliwood, using it will essentially prevent Darin from ever scoring a chance critical on Hector.
—Darin's battle quote
- Vs. Eliwood
Eliwood: Darin! Your treachery ends here!!
Darin: Ha ha ha ha. I will never fall to the likes of you!!
- Vs. Hector
Darin: Oh... You're Marquess Ostia's younger brother...
Hector: I couldn't care less if you've a grudge against Ostia. I'll put up with your treachery no longer!
Darin: Heh heh heh... Ostia is no longer my main concern... Nor is the whole of Lycia... The only goal worthy of my attention is the entire world!
Hector: You're mad!!
- Vs. Lyn
Lyn: Are you Darin? My grandfather... You tried to...
Darin: What? Who are you?
Lyn: I am Marquess Caelin's granddaughter, Lyndis!
Darin: Oh...that senile fool? ...That doddering wreck dared disagree with me... I was so happy to be rid of him.
Lyn: You're a dead man!
—Darin's death quote
- Judging by that Darin was pursuing Priscilla and that he already has a son, it can be assumed that Darin is either a widower or unfaithful to his wife.