These are the only mentions of Boreale and Kaurava in Chaos Rising, along with the aforementioned three companies line:
Tarkus: Another fallen brother.
Veteran Lucanus, also of the Fifth Company.
Martellus, what do the rolls say about Brother Lucanus?
Martellus: Killed in the Kaurava campaign.
Cyrus: I was at Kaurava. I recall no Lucanus.
Cyrus: You are doing well, Blood Ravens. You must have paid attention when I trained you.
Tarkus: It was Kaurava that damned you, I think.
You allowed a reversal of war to defeat you.
Cyrus: Spare me your moralizing, Tarkus.
Kaurava was no reversal -- it was a slaughter.
A slaughter caused by the incompetence of Indrick Boreale.
Storm of Lost Stefanus
This prized storm bolter was turned against forces of the Imperial Guard in the Kaurava Campaign. Its original owner, Sergeant Stefanus, never returned from Kaurava, nor was his holy gene-seed recovered.