A word of warning, though, to those unfamiliar with Games Workshop: opening the box may be very intimidating to some. There is no neat little baggie of playing pieces. Instead, one finds sprue after sprue of unassembled plastic models. Workshop minis are relatively easy to assemble, and none of the models in this box set are going to cause any trouble for anyone that has any modeling experience whatsoever, but there will be quite a few hours of assembly before gameplay can begin.

Right… how do you play, then? Well, players alternate activating their units (which consist of up to three models), so you’re never going to be waiting around for a go. When it’s your turn your unit will be able to spend one of its tactical points to perform the following actions: advancing one hex, running two hexes, shooting, close combat or a model can consolidate itself to join up with a new unit. More than one-half of the Ultramarines' muster (at least one hundred thousand Ultramarines, and thousands more soldiers) died during the Battle of Calth, and many more likely perished during the years of fighting in the Underground War that saw the scattered remains of the Word Bearers flee beneath the catacombs of Calth. However, the Word Bearers ultimately failed to eradicate the XIII Legion, and Guilliman lost little time in embarking his remaining forces to Terra, to intervene in Horus's planned overthrow of the Emperor. This was to prove decisive to the outcome of the Horus Heresy; although the Ultramarines were unable to reach Terra in time to take part in the battle, word of their approach reached Horus, forcing him to gamble by allowing the Emperor to teleport aboard Horus's ship. [Needs Citation] Enlightenment and knowledge are sundered; the Age of Darkness has begun in earnest. The Emperor’s glorious vision for humanity lies in ruins as his favoured son, Horus, has rejected his father’s light and embraced the corrupting tendrils of Chaos. Civil war has broken out amongst the Space Marines — once brothers, fighting side by side as the galaxy’s protectors, they are now a force divided. Some remain loyal to the Emperor, others have sided with the Warmaster. Nothing is certain, everything is at stake, and the Imperium is split down the middle... It would take several Terran years for the remnants of the Ultramarines fleet to return to the Veridian System after the Loyalist survivors rode out the storm. Unfortunately, the forces of Chaos left on the planet also fled underground as well. Vetanus vowed that the Ultramarines and their allied Loyalist forces would continue to fight until every last Traitor on Calth had been exterminated. Thus began the phase of the conflict that would be remembered as the "Underworld War." The Word Bearers' use of Calth's orbital defence platforms against Calth's sun destabilised it, tore away the outer layers of its photosphere and threatened to cause it to explode as a supernova. The Veridian System's star, its colour changing from a bright yellow to an angry blue as its internal composition shifted, immediately suffered a flare trauma, and shortly after unleashed massive solar flares that irradiated Calth with lethal levels of radiation and stripped away its once dense oxygen-nitrogen atmosphere.

An instant later, the entire bridge erupted in an explosion of phantasmagoric viscera, blowing out its armoured viewing dome and blasting its occupants into the void. At a stroke, the Ultramarines were bereft of their beloved Primarch and their beleaguered fleet had lost its flagship. What occurred next had no known precedent in the annals of the Great Crusade, for while the scions of the great Navigator Houses of Terra had some inkling of what lurked beyond, such knowledge was denied to all others, even the Legiones Astartes. The thing that had manifested on the bridge had exploded in a fountain of gore and the force of the detonation had breached the hull. The Primarch, who had been standing at the very eye of the storm, had been blown upwards and outwards through the breach in an instant, the writhing remains of the monster into which Lorgar's lithic avatar had transformed snaring his mighty form in a thrashing mass of spiralling pseudopods and motile shadow.

The Primarch's intervention saved the lives of dozens of his sons. It fell to them though to persuade their gene-father to cease his furious battle on the flagship's outer hull and to rejoin his warriors within. The Primarch had fought for ten hours without respite, his sons believing him lost. Now he was returned to them, and for the first time since the beginning of the Battle of Calth, defeat and extinction did not seem inevitable.

The Shadow Crusade

The second big gift is a really awesome special armor set that ONLY CURRENT OWNERS OF THE GAME will have access to in Multiplayer. If you have Betrayal at Calth in your Steam Library, you'll get this armor! Fortunately, the Furious Abyss was intercepted in the void before it reached Macragge by an ad hoc force led by the Ultramarines Captain Lysimachus Cestus and was destroyed, though at the cost of every one of the Ultramarines' lives.