I wrote a short fic about this scene! (Thanks @tecchiiiiii for the heartache and angst… this one bubbled out of my SOUL despite my best attempts to keep it caged inside.)
Snippet:
Robin collapses to the cold hard stone, drained of everything, even tears. His knees throb, but it is like nothing compared to the ache behind his ribcage, suffocating him. His best friend, his lover, his king doesn’t acknowledge him. Even when he calls his name, shouts it to echo through the cobwebs in the lofty ceilings of the hall - even when he pleads, there is no response.
Chrom’s piercing red eyes go through Robin, burning wrong from beneath stern eyebrows. This is wrong. It’s all wrong - he expected to return to a kingdom ascendant, not a palace of rubble.
What did he sacrifice for? What was his sacrifice for, if not to protect Chrom and his descendants?
What was it for?
You can find the rest on AO3: angst here