Jace’s voice breaking on ‘where thou diest will I die’.
Alec hesitating in the middle of his oath because he knows there’s no turning back.
Jace telling the werewolves that they can have their vengeance but that he needs to get to Alec first.
The entirety of their final test and Alec’s interactions with Izzy (I know people had their doubts, but the flashbacks were so good and the actors were amazing).
The way they looked at each other a moment after Alec woke up.
“It’s all right, Alec. What matters is you’re back.” and that sad little smile and Alec being too weak to follow him.

This is all printed on the inside of my eyelids. It’s there every time I blink. I will never be free.