We all know that undead creatures exist (such as zombies and skeletons), but...

[Rekenber]

I think it was Ul'dah or some precursor city to Ul'dah that Sil'dah was fighting, but I'm not 100% sure on that.

As for the Dragoon quest giver, he was the Azure Dragoon, although his true reason for retiring as a Dragoon all together wasn't due to any injuries, but for another reason which I'll refrain from mentioning due to spoilers. His protege ended up becoming the current Azure Dragoon, and is a hyur as well.

[Alenore]

snip

War og the Mai had Nym, Amdapor and a third (yet) unnamed nation fighting each others. The thrid nation survivors ended creating Belah'dia after the war, which in turn made Ul'dah and Sil'dih after.
Sil'dih did not take part in the War of the Magi.

However, I'm pretty sure Sil'dih created Undead to fight Ul'dah.

As for the Dragoon quest giver, he was the Azure Dragoon, although his true reason for retiring as a Dragoon all together wasn't due to any injuries, but for another reason which I'll refrain from mentioning due to spoilers. His protege ended up becoming the current Azure Dragoon, and is a hyur as well.

Without spoiling too much, we see in this patch Main scenario quest that being Hyur doesn't seem to be a problem to have important positions in Ishgard.

[treuhavik]

However, I'm pretty sure Sil'dih created Undead to fight Ul'dah.

Yes. Here's some dialogue from the monk quest-line I found a while back on a deceased thread somewhere:

"I need hardly mention that Sil'dihn civilization is now centuries dead.

Sil'dih was plunged into chaos in the wake of King Lalawefu's demise─or the King of Springs, as he was known. Despite the success of his economic reforms, the tax increases he imposed did not sit well with his subjects. This, coupled with a prolonged sequence of untimely droughts, fomented unrest among the people and in time sparked violent unrest throughout the kingdom. Sil'dih was not alone in its want for water. Ul'dah, too, felt the effects of the droughts.The sultan at the time, Sasagan Ul Sisigan─ Ah! But perhaps you recognize the Ul name? The current sultana, Nanamo Ul Namo, represents the second Ul dynasty. She is Sasagan's distant descendant. Now...where was I? Ah, yes! Right, so, Sasagan ordered an attack on Sil'dih to claim the water resources discovered as a result of Lalawefu's flood control acts.

But the royalty and nobility of Sil'dih would not remain idle. They mobilized their nation in the face of this crisis, and the people fought with great tenacity against the Ul'dahn threat. The full strength of both nations met in battle, and the end result was an arduous protracted conflict. Though arguably more desirable than surrender, the ruling Sil'dihn elite took little pleasure in having succeeded in uniting the theretofore querulous citizenry to fight. For despite all they accomplished, every day spent waging war dragged the nation's financial affairs─which you will recall had only just been brought under control─back into the mire.

To bring an end to the long military deadlock, Sil'dih devised and set about implementing a perverse yet ambitious strategy. It sought to zombify the deceased among its army, that they might fight again. At first, it appeared to have worked. Yet at the height of hostilities, the Sil'dihns lost control over their necrotic creations. The undead turned on their masters, and before long the zombification had spread to a majority of the population. Ever knowing an opportunity when they saw one, the Ul'dahns grasped this turn of events to justify their war─now proclaiming it a crusade to send these zombies to Thal. After seeing to the extermination of all zombies outside the city, they then sealed the gates of Sil'dih, entrapping both the living and dead within.

And that, in brief, is a history of the fall of Sil'dih. I only pray that your feeble mind is able to retain it." - Erik

[Baithin]

War og the Mai had Nym, Amdapor and a third (yet) unnamed nation fighting each others. The thrid nation survivors ended creating Belah'dia after the war, which in turn made Ul'dah and Sil'dih after.
Sil'dih did not take part in the War of the Magi.

However, I'm pretty sure Sil'dih created Undead to fight Ul'dah.

Sorry, got my timeline confused. You're right, Sil'dih did war against Ul'dah and that's where the undead came from.