Eleventh Chapter (Expunged): The Eleventh Chapter in the records of the first founding chapters has had all records expunged from the libraries of Terra. The origins, Primarch and homeworld are unknown, although they were once listed. It is possible that this eleventh chapter turned traitor, although this is highly unlikely as it is usually listed as "Excommunicate Traitoris". What is more reasonable is that the chapter's gene-seed was too corrupt by the scattering of the Primarch's and so the chapter was disolved to remove the taint.
Source: Codex: Space Marines, 3rd Edition by various
Submitter: IBBoard
Hive World Terra