The captain of Desaix's guard, Slayde reached his position years prior, when he met Desaix in a discreet location, and agreed to help dethrone the Zofian royal family by killing the remaning royal children, Anthiese and Conrad, along with any possible witnesses, in exchange for a greater position of power. Slayde attempts to do so by burning the villa they are staying in, though the royal siblings manage to escape and go into hiding.
Some time later, when the village children from Ram Village decide to see some knights led by Slayde in the nearby forest, he demands that the children and the other residents of Ram village give them lodging and food while threatening Faye, being stopped by a young Alm. He recognizes Celica, and tries to capture her. However, Mycen arrives and and forces Slayde to retreat. Though defeated, his awareness of her location forces her to leave the village.
Years after the incident in Ram, during the uprising of the Deliverance, Slayde fights along side Desaix in defense of Zofia Castle, aiding him in his battle against Alm at Zofia Castle, setting up a double of Desaix to lead the battle in order for the real Desaix to escape.
Echoes: Shadows of Valentia
Slayde survives his initial defeat at Zofia Castle, being driven out of it. While hiding around the castle grounds, he happens upon some of the Duma Faithful lurking around, having just made a failed attempt at capturing Celica.
Slayde uses this opportunity to convince them to allow him to serve the Rigelian empire. In exchange, Slayde reveals information about a certain village, implying it to be the reason behind Delthea's kidnapping. Following the aftermath of Desaix's death, Slayde participates in the battle to defend Rigel's northern fort, though he is killed by the Deliverance's forces.
Slayde is shown to be a corrupted and greedy knight who cares only for himself and power. He is also willing to kill children just to bring Celica to Desaix. He is also shown to be arrogant, believing in his rank makes better than anyone. He also will betray any groups he is associated with if it suits him.
Slayde: I recognize you... You're those bumpkin brats from the village in Ram Woods.
Alm: Huh? ...This is the knight who tried to kidnap Celica!
Slayde: You whelps deprived me of a prize I most desperately needed. Hear me well runts. My name is Slayde...and today, I in turn shall deprive you of your lives!
—Battle quote in Act 1
—Defeat quote in Act 1
—Battle quote in Siege of Zofia Castle
—Defeat quote in Siege of Zofia Castle
- He shares his Japanese name with a character from Fire Emblem: Genealogy of the Holy War.
- In Echoes, Slayde is the only minor boss to be fought three times.