From Lexicanum

The Barghesi are an alien race that inhabits the Grendl Stars, a constellation in the Eastern Fringe.¹ They are known to be 'hyper-violent'.

According to Imperial Records, the Iron Lords Marines Chapter proved instrumental in confiding the Barghesi to the Grendl Stars, and also in preventing the destructive biological potential of the Barghesi from being harvested by Hive Fleet Kraken.²

Sources

• Warhammer 40,000 4th Edition Rulebook, p. 139
• ¹: Warhammer 40,000 5th Edition Rulebook, p. 117
• ²: Codex: Space Marines (5th Edition), p. 29