The Legio Vendettica is an obscure Titan Legion of the Collegia Titanica. Very little is known about this specific Titan Legion in Imperial records, save that its origins lay on Mars. The only known reference to the Legio Vendettica dates back to the 31st Millenium and the dark days of the Horus Heresy.
At the time of the Schism of Mars and the subsequent blockade of the Red Planet by the Imperial Fists Space Marine Legion, the Legio Vendettica maintained an extensive armoury depot in the eastern part of the Mare Hadriacum.
This facility was used by the Traitors of the Dark Mechanicum aligned with the Traitor Fabricator-General Kelbor-Hal. It was raided by the Loyalist Mechanicum resistance force known as the Omnissian Faithful.
- Heralds of the Siege (Anthology) edited by Nick Kyme and Laurie Golding, "Myriad" by Rob Sanders, pg. 40