Crusade of the Ophidium Gulf
Raimer led the 90 Black Templars marines aboard the Ophidium Gulf in a crusade into a treacherous part of space in the Galactic South, known as the Veiled Region. Here they discovered some inhabited worlds. The primitive aliens living there worshipped a god they called the "Voice of the Emperor".
While trying to find out what the nature of this god was, Raimer destroyed the alien temples and moved on to the core planets of the system. While doing so, they discovered that most of the worlds had already met a destructive power greater than Raimer and his men. During their trek to the core planets, the sensorium of the Ophidium Gulf detected a small fleet of vessels breaking orbit of one of the devastated worlds. Augers determined that these ships were of the Dark Angels Chapter.
After making contact with the fleet, Raimer offered to fight alongside the Dark Angels to capture the alien's leader, the "Voice of the Emperor".
The Dark Angels' commander was reluctant to accept the help of the Black Templars but did so anyway. During the last battle for the stronghold of the "Voice of the Emperor", Raimer's marines broke through the alien defences and captured the alien leader. This so-called god was clad in ancient black Power Armour without any livery or panoply. Raimer now suspected why the Dark Angels were reluctant in accepting their help and fell back to his strike cruiser and chained the prisoner in the most secluded vault aboard.
Almost immediately the Dark Angels demanded that the prisoner be delivered to them. Raimer at first refused this, but when the ordnance sensoria warned him that the Dark Angels fleet was bringing its weapons to readiness, he had to comply, for his lone strike cruiser was no match for the fleet before it.
When the Dark Angels received the prisoner they broke orbit and left the system without a word.
The fate of the Ophidium Gulf remains a mystery. The last that was heard of it was a single communication when en route to the system jump-point. There has been no contact with Castellan Raimer since.