Emilio Rachan (b. 29?? - d. 3028) was a rogue ComStar Precentor whose plot to find a missing Star League memory core resulted in the temporary declaration of the Gray Death Legion mercenary unit as outlaws.
After ROM determined near the end of the Third Succession War that the long-lost SLDF cache on the Free Worlds League planet Helm, recently assigned as the land-hold of the Gray Death Legion, was real and that it very likely also contained a Star League Memory Core, Primus Tiepolo selected Rachan to oversee efforts to eliminate the threat to ComStar's holy mission. With Blessed Order believing the mercenaries would not be receptive to direct manipulation or bribery, Rachan was directed to engineer a minor civilian "incident" to defame the Legion and justify their removal before revealing the existence of the stockpile to League government, the Order placing a division of the ComStar Guards and Militia on stand-by to infiltrate the League's recovery efforts to ensure the stockpile and the memory core were either destroyed or fell into ComStar's hands. 
Rather than approach the League government directly, Rachan opted to contact several rebellious lords in the Free Worlds League, promising them a portion of the stockpile in return for their assistance, making no mention of the existence of the library. Rachan would ultimately connect with Lord Garth of Irian, promising the greedy Garth enough 'Mechs to overthrow Captain-General Janos Marik in return for providing Rachan a position any new government. 
Rachan arranged with the Gray Death member-traitor Graff to allow the transport of an unknown -- and possibly nuclear -- explosive device inside the domed city of Tiantan, the capital city of Sirius V. Using BattleMechs painted to look like Gray Death 'Mechs, Rachan, in concert with Lord Garth's efforts, staged footage to make it appear that the Legion had, under a flag of truce, destroyed the domed city, exposing the few survivors to Sirius V's toxic, frigid atmosphere. Appalled at the act, the Primus and the First Circuit ordered Rachan's immediate excommunication and extermination by ROM. 
Lord Garth's efforts continued the plot, which involved having the Gray Death jump to the planet Marik under the pretense of meeting with the Captain-General. Upon arrival, the Legion would instead have immediately been arrested and charged with the destruction of Tiantan. However, Gray Death commander Grayson Death Carlyle, sensed that something was amiss. With the majority of the Legion's dependants and troops who had not been assigned to the two-week Sirius V campaign the Legion's landhold on Helm, Carlyle elected to move his combat troops to their base on Helm first.
Upon arrival, the Legion found itself under attack and pursued by Lord Garth's forces across several hundred miles of the planet.
Death and Legacy
In the ensuing land campaign, Rachan's quest to claim the missing Star League cache failed, the Gray Death Legion instead obtaining a copy of the memory core at the underground base on 1 April 3028. Rachan was killed in the fighting on Helm.
Shortly after the events on Helm, ComStar disavowed all Rachan's actions. Publicly Primus Tiepolo sent a message to the Captain-General branding Rachan a renegade operating of his own accord, also authorizing massive compensation payments to the survivors of Sirius V as a gesture of good will. Privately however, Tiepolo was utterly appalled that Rachan had both failed to recover or destroy the memory core and that he had taken such a direct role in the affair, placing ComStar's vaunted neutrality at risk.
Word of Blake interjections in the Secular ComStar's historical overview of the affair insist that Rachan's only deviation from the plan out-laid by Primus and the First Circuit was the extent of the "incident", the Blakist writer expressing as much horror for the loss of a domed city dating back to the Star League era as the millions killed in its destruction. 
- ComStar, pp. 53-54 "History of ComStar - The Tiepolo Years - Circles within Circles"