Assault on Darktide Roost

Getting to the island for the first time:

Take a flight path to Pinchwhistle Gearworks, or get there by other means if you don't have it already.
Mount up on Azure Water Strider.
Run east around the coast to Shadowmoon Valley.
Go up on land on the west side of Socrathar's Rise.
- Mobs are level 100. Go up the hill and keep making your way up the right side to the flight path.
Get the flight path at Socrathar's Rise.
Drop off the cliffs behind the flight path and continue east to the island.
Get the flight path on the island, and now you're connected with the rest of the Horde flight paths.

The objective pops up as soon as you're in range of the island, but isn't all that clear. Kill mobs and click on eggs to fill your progress bar, as already mentioned by jujuness.

• Location: For Horde, continuing on the road from eastern Talador will take you into Shadowmoon Valley. Or, take Azure Water Strider from the coast of Spires of Arak along the southern coast of Shadowmoon Valley until you hit the large island. There are flight paths at both Socrethar’s Rise and Darktide Roost.
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• Rewards: [currency=823 amount=800]
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• Related achievements: You Can't Make a Giant Omelette..., You Have Been Rylakinated!, I Was Framed!
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• Related Reputation: [faction=1731]
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• Related Garrison Invasion: Shadowmoon Invasion!
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• Related Loot: [item=119400] from Avalanche, [item=119411] from Slivermaw, [item=119364] from Nagidna

[h3 toc=false]Strategy and Mob Percentages[/h3]
Kill [npc=78148] for [item=116978] which can power up [npc=86085] for a DPS boost. Also loot [item=115020] from [npc=78999] so you can jump up to the top of the mountain and loot [object=235826] for a ~7% gain. Eggs are a good source of quest progression if you feel undergeared to kill mobs.

[toggler id=1 hidden]Mobs that increase progress % per kill (click to view)[/toggler][div id=1 hidden][pad][pad]

[pad][div] [/div][pad]

Kill Iron Horde Vignette  (10% each)
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Avalanche

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Slivermaw

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Nagidna

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Collect Giant Rylak Eggs (5% each)

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Collect Large Rylak Eggs (3% each)

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Collect Rylak Eggs (1% each)

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Kill Iron Horde Elite (3% each)

[pad][div] [/div][pad]

Kill Iron Horde Boss  (2% each)
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Assistant Fexfuse

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Captain Killrath

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Razz Ricketroz

[/div][/div]

[pad][div] [/div][pad]

Kill Iron Horde Soldier  (1% each)
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Darkwing Matron

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Darktide Rylakinator-3000

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Darktide Engineer

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Darkwing Adolescent

[/div]
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Darktide Pilferer

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Darktide Guardian

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Ra'ka Bloodspear

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Darktide Windstalker

[/div]
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Controlled Darkwing

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Darktide Machinist

[/div][/div]

[pad][div] [/div][pad]

Kill Iron Horde Peon  (.3% each)
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Iron Peon

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Darkwing Whelpling

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Injured Rylak (1% each)

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Burn Banner (2% each)

[/div]

I hate to seem dense, but how do you even GET there?