The Inner Circle was a mysterious secretive organization. Many Dark Angels members never learned even the slightest truth about it before dying in battle. The same was true for those who joined the Inner Circle.
Different ranks within the Inner Circle knew different things, and even members of the same rank could possess vastly different secrets in terms of importance and content.
This led to some rather bizarre situations. For instance, two Dark Angels might have fought together for countless years, earned innumerable merits, and learned secrets that could not be put into writing. Both became members of the Inner Circle, yet because they held different ranks and positions within it, neither ever realized the other was also part of the Inner Circle.
One knew that some dangerous technology was kept deep within The Rock.
One knew that the Dark Angels possessed an organization dedicated to purging Fallen Angels.
As time passed, the two warriors developed profound suspicions of each other in their daily interactions.
"Hey, you weren't assigned patrol duty that day. So why were you patrolling the XX floor?"
"Hey, during the XX campaign, you left without saying goodbye. Before you went, you even took a great deal of special ammunition. What exactly did you go off to do?"
The two fell silent for a long time, screaming inwardly.
Damn! He's probing the Dark Angels' untouchable secrets!
They immediately recalled the secrecy regulations, drew their guns, and opened fire. After a burst of flames, the two lay on the ground without a sound. Before they died, their minds were filled with disbelief at their brother's betrayal.
"I never thought... that the brother who had fought beside me for so long... was actually a spy investigating the Dark Angels' secrets..."
In the end, the matter was reported to Azrael.