What the Cold Wind Brings...

I've come to Warsong Hold many times on different characters, and every time, without fail, there were waves of sky darkeners coming in fighting the guards. I never once saw any Ith'rix nor his carapace, but I'd never searched for it before, either.

Now that I'm searching for some last quests in Borean Tundra, I find out about this one and go check Warsong Hold to discover a sight I've never seen before: no sky darkeners attacking. I've been waiting outside for a while now, and they don't seem to be coming.

I wonder if the battle starts when a character who has not been present for the battle enough times comes near? If so, it would make sense that I don't see them now, as this character I'm on now has been present more times than any of my other characters. And it could also explain people saying he has a 30 minute spawn timer and others saying they waited much longer and haven't seen him. Maybe if a character present still has some rounds left, he will spawn every 30 minutes as long as they stay in the area.

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I just waited in front of Warsong Hold for around 15 minutes, and they suddenly started coming in at the same time as the zeppelin arrived. There was one lv 67 on the zeppelin, who claimed to have never been to northrend on that character. We waited through the waves and got Ith'rix's Hardened Carapace. :)

on a side note: I did see the warsong captain's health drop quite a bit during the fight. I found that casting abolish poison and lifebloom helped him immensely. He may have survived without my help, but if you have healing spells, you might be advised to use them just in case.

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after a few hours of observing what happens and asking several people to come to Warsong Hold, I have made the following observations, with a fair amount of accuracy:
1. The sky-darkeners will only start attacking at the same time as a zeppelin shows up.
2. They only start attacking at the same time as a lv 68 or higher level character enters Borean Tundra.

So it would seem that the event does indeed begin when you first arrive in Borean Tundra. If you miss it, you have to get somebody else to start it for you, or wait until someone new comes on the zeppelin from Durotar.

All you need to do to get this quest is go to Warsong Hold, sit in front of the keep, and wait. It will start, Ith'rix will eventually spawn, and you will be able to loot the carapace once he's died.

1. 
   
2. This event is not triggered by anything. It is on a timer, and based on several other comments combined with my experience, it looks like it's either every 45 minutes or on the top of the hour (mine started at 2:58 pm).
3. 
   
4. You don't need to do anything special to make sure he spawns. He showed up at 3:07, after I'd been killing the attackers for about 10 minutes, and had kept everyone alive. Based upon another comment, if the defenders are all dead, it should not matter.
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6. This has not been affected in any way by the level squish or the introduction of Chromie time. I did it on a max level disc priest during patch 9.0 in "present" time.
7. 
   

The quest starts when the Warsong Captain yells, "Marksmen! Front and center! Scourge attack incoming!" (This event did indeed seem to start in unison with a zeppelin arriving.)
It takes a while for Ith'rix to appear (there were about 7 - 12 swarms of non-elites, I wasn't really counting though).
I DID participate in the battle against the swarms.
You know Ith'rix the Harvester appears when he yells, "I will take great pleasure in tearing the forces of the Horde apart... limb from limb and piece by piece..."
I did participate in the battle with Ith'rix, although I was level 80 when I did so.
After the defeat the Warsong Captain yells, "The Nerub'ar have been punished for their transgression!" then "Let the forces of the Lich King gaze upon the carcass of this wretch and know that the Horde will not relent!" He then says, "Gather, soldiers! Gather and take your trophies from the carapace of the enemy!"
The carapace will drop where Ith'rix died. It sticks around for about 4 - 5 minutes before disappearing.