This flashback touches on the events that happened in Elehiya which you can read here: kazrowe.gumroad.com/l/boHZU Bahram and Azrael have a really complicated dynamic. Elehiya goes into it in greater detail.

Azrael remembers the one time he and Nikita kissed when they were alive. AZRAEL: "But... But... he just wanted my attention. As soon as he saw he wouldn't get it on his terms, as soon as I questioned him," he remembers Bahram's meltdown after then kiss, "or surpassed him," flashback to their quest for the Elixir when Nikita corrupted himself in Sector Five, "I became the enemy." Azrael remembers the rift, Nikita standing before him beneath it, his bright red eyes staring at him with searing hate as hundreds of colorful souls are sucked into the rift. AZRAEL: "A convenient enemy he can blame for all his own shortcomings." Nikita becomes Bahram, screaming, overcome by his own corrupted energy and power, his teeth sharpening into fangs. Then we see Azrael sitting alone in Sector Thirteen, mask obscuring his face, knees pulled in to his chest and looking very small. AZRAEL: "And all I wanted... was for someone to care about me."