Blagden is likable.
"Dragons, like wagons,
Dragons, like flagons,
But while two hold beer,
The other eats deer!"
"... And little birds too."
— Blagden to Saphira
Blagden was a white raven who lived in Ellesméra. Blagden saved the life of the elf king, Evandar when he lost his balance and his sword during a duel with an Urgal. After Blagden pecked out the Urgal's eyes, the elf king blessed the raven with intelligence, long life, and other unintended effects. This blessing allowed Blagden to sense the future, but was counteracted because he always spoke in riddles. Another effect the blessing had on Blagden was that his feathers changed color from black to white.
During Eldest, Blagden was seen saying 'Wyrda!' all the time.
Blagden did not appear in Eragon or Brisingr, but it is important to note Eragon mentioned in Brisingr both Blagden and his riddle to Oromis after Oromis related the truth of his parentage. Oromis asserted Blagden is a fickle creature with a penchant for eavesdropping on those he does not entirely trust.
In Inheritance Blagden also tried to aid Queen Islanzadí at Urû'baen in her duel with Lord Barst, attempting on several occasions to peck out his eyes. He was driven off by a blow from Barst's mace.
After Islanzadí's death, Blagden was seen flying overhead, singing sadly.
Blagden then aided Roran in his fight against Barst, successfully gouging out one of his eyes before having his wing broken by Barst's mace. He later returned to Du Weldenvarden and was seen with Arya after she became queen.
Blagden lived in Ellesméra at the court of Islanzadí. Blagden told this riddle to Eragon in Eldest:
"By beak and bone,
Mine blackened stone
Sees rooks and crooks
And bloody brooks!
Son and father alike,
Both as blind as bats.
While two may share two,
And one of two is certainly one,
One might be two."
It seemed Blagden was referring to this:
The first verse might indicate the Battle of The Burning Plains, as this was before the battle. It would also make sense because the battle took place next to the Jiet River, which would explain the "bloody brooks".
The second verse might be saying that Brom, Eragon's father, and Eragon himself both missed the obvious when talking to others.
The final verse is a comment on Eragon's parentage and foreshadows the revelation, in Brisingr, that Brom is Eragon's father: Like any siblings, Murtagh and Eragon share parents (while two may share two). Their mother, Selena, was certainly the same (and one of two is certainly one). But their father may not necessarily be (One might be two). Brisingr showed that this is indeed the case - they are half-brothers: while Murtagh is the son of Morzan by his wife Selena, Eragon is not, and Brom was his true father.
Throughout Eldest, Blagden cried "Wyrda" a total of five times. "Wyrda" in the ancient language means "fate".
After Eragon arrived in Ellesméra and met Islanzadí.
Before Arya recounted story of the Menoa tree, where the brightsteel was later found.
After Arya and Eragon discussed the baby he blessed (Elva).
Right before Eragon was transformed during the Agaetí Blödhren.
After telling a riddle that, while Murtagh and Eragon share the same mother, Morzan was not his father. (see above)