Can someone please explain what he mean by my only beacon? What does that mean (￣∇￣...

idk, beacon? flare?? is it light? so she's his only light???

so basically he'll die if no one believes in magi, and she's the only person left who still believes.

I think it means ‘beacon of light’ so she’s the only light in his life :)
maybe my brain just corrected it to the more romantic version ;-;