Battle of Calth - Desperate Gambit: Fortunately, amidst all this negative information, somehow Magos Tawren managed to discover a killcode that her former mentor Hesst had hidden within a secure data-engine at the Zetsun Verid Fleet Yard that had then been closed off from the rest of Calth's planetary network. This data-engine was the manifest Cogitator of the Cargo Handling Guild, which was located in a secured bunker in the industrial zone between Numinus Starport and the Lanshear landing grounds. It was responsible for running cargo operations for both Numinus and Lanshear, and thus was more than powerful enough to manage the data load of the planetary weapons grid.As a civilian Cogitator, it was not a primary military target during the Word Bearers' initial assault and Hesst had been able to take advantage of this before his death. Though he had suffered from the painful overload of the data-shock that was killing him, Hesst had managed to clean this data-engine with his killcode and then keep it severed from the broader planetary network. Contacting Guilliman aboard his flagship, the Macragge's Honour, Ventanus apprised his Primarch of the new developments.He informed him that the enemy was controlling Calth's planetary defence grid using a captured data-engine on one of the surviving orbital platforms at the Zetsun Verid Yard. Magos Tawren would be able to purge the system of the Word Bearers scrapcode using this Cogitator, but could not access the Cargo Handling Guild's data-engine while the Word Bearers remained in control of the platform. They would need assistance from the Ultramarines in orbit in order to gain control of the platform and perform the purge of the planetary weapons grid.Several plans were debated aboard the Macragge's Honour by the Ultramarines' commanders. Shipmaster Hommed recommended a ranged bombardment of the platform using the flagship's main weaponry. The Macragge’s Honour certainly possessed the needed firepower. Chapter Master Marius Gage seconded the suggestion. But if they did not make a direct kill of the Word Bearers holding the platform with the first salvo, there was a real danger that the enemy would retaliate using the planetary defence grid and finish off the Ultramarines' flagship. Chapter Master Klord Empion of the 9th Chapter opted instead for a close attack plan: bring the flagship back to full power, throw off the enemy Cruisers surrounding it and head straight for the orbital platform and eliminate it at close range, by ramming if necessary. Unfortunately, the moment the massive flagship began to move it would again become a target for a planetary weapons grid that could annihilate it all too easily. Finally, Chapter Master Gage’s alternative plan was considered: reroute all of the crippled warship's available power into its teleporter system and teleport a Kill-squad of Ultramarines, possibly two if the power lasted, directly to the Zesun Verid Yard to take control of the orbital platform from within.Led by Roboute Guilliman himself, the first Kill-squad of 50 Ultramarines assembled at the flagship’s teleportation terminal. The transverse assembly deck of the Zetsun Verid Fleet Yard was their chosen teleport destination. It was the largest interior space on the orbital platform, and thus made it less likely that imprecision in the teleport would lead to a large number of deaths. Their assault target was the Zetsun Verid Yard’s master control room, two decks up from the transverse assembly deck. Given the risk factor and the atrocious error margins of teleporter arrays, the teleport was considered a success. 46 members of the Kill-squad appeared with Guilliman on the transverse assembly deck of Zetsun Verid Yard. Only 4 Battle-Brothers had been lost during the transition and failed to rematerialise.The Kill-squad immediately encountered heavy resistance from the Word Bearers, but with Roboute Guilliman at the fore, the enemy forces balked before the sheer killing power of an enraged son of the Emperor. With righteous fury the Primarch killed over a dozen Word Bearers single-handedly, including the daemon-possessed Astartes of the Word Bearers' vaunted Gal Vorbak. Though 8 Ultramarines were lost in the assault, the Kill-squad managed to break through into the master control room. A heavy barrage of Bolter fire greeted them as the real fight awaited. Within was the XVIIth Legion's First Captain Kor Phaeron, Black Cardinal and Master of the Faith, who ordered his men forward. Then he flew at Guilliman, summoning forth blasphemous energies from the Warp to assault the Primarch. Guilliman roared his challenge and charged.