Alec Lightwood: Magnus, what is it?

Magnus Bane: It’s just… sometimes… I lose control. (Magnus’s warlock mark/cat eyes are showing)

Alec Lightwood: Magnus… they’re beautiful. You’re beautiful.

(Flashback/Bonus scene from 2×07)

From Shadowhunters – Season 2 Episode 18: ‘Awake, Arise, or Be Forever Fallen’ (2×18)