Showdown at Corticant - Prelude to battle and early Ynnari advance

While general Veers was planning his grand assault on Corticant to take ground and hunt down the webway portals, he was unaware of the opposing forces' building up against him. The Ynarri and their eldar allies were able to completely disguise their military build up by hiding their forces in the webway. The force the aeldari were about to unleash on the Imperium in order to take the evacuation site and device chamber was massive, and almost equal to the forces employed by the xenos at the battle of Sentinel many years before. 

On the Imperial side, Veers planned a simple but brutal advance using his Novgorod and Valdograd regiments, supported by a warhound from the Legio Titanicus, as well as a full battalion of super heavy tanks. From his start points this force would  fan out into the wastelands, harrying and pursuing any eldar forces in order to throw a defensive ring around the inhabited zone, while systematically destroying the access the eldar enjoyed to the world.

On 1905.020M42 the Imperium began moving its forces into position, but before Veers even got to start the attack, the Ynarri struck. Pouring from the webway the Ynarri raced south from their remaining positions on Corticant during the night with no regard for consolidation of their positions. The massive concentration of force included massive Vampire Hunter aircraft, a full spearhead of Fire Prisms and an entire Wraith Host.

This awesome eldar army simply smashed through Veers' screening line and before the Imperium could react, the Excavation site had been secured, along with Bymarsh and Blackhollow. Now the Aeldari had to hold on, long enough for them to deactivate and make safe the necron device. Long enough for the Imperium to respond.

To prevent an their enemy from launching a two pronged attack, the Aeldari used their Craftworld allies to launch a spoiling attack north east towards Lake Hartford. If the eldar could reach the shore, the Imperial Army would be sliced in two, and badly needed resources would need to be redirected north to counter this immediate threat to Veers' HQ. If successful, this diversion would prevent the Imperium from even being able to counter attack in strength at the all important Excavation Site. The scene was now set for the Showdown at Corticant.


Showdown at Corticant Order of Battle

Imperium

Valdograd Super Heavy Tank Battalion (Shadowswords)

Legio Titanicus Warhound Scout Titan, 

3 Valdograd Artillery Regiments

2 Novgorod Armoured Regiments

6 Novgorod Infantry Regiments

1 Fraeteli Militia Regiment

14th Corticant Air Wing (Imperial Navy)

16th Stormtrooper Regiment


Aeldari (estimated by Imperial sources)

Yvraine, the Yncarne and the Visarch

Wraithguard

Grotesques and razorwings

At least 30 Harlequin bikes

Eldar rangers

Dire avengers in wave serpents

Fire dragons in wave serpents

Spearhead of fire prisms

Air wing of Crimson Hunters

2 Vampire Hunters