gathering

sky
They gazed up at the twilight sky.

hour (often figurative)
in the twilight hour before dawn
He had the courage to spend his twilight hours acknowledging his misdeeds.

world (figurative)
the twilight world of the occult

zone (figurative)
the twilight zone between living and merely existing

years (figurative)
a forgotten man who spent his twilight years alone

at twilight, in the twilight, into the twilight
She stared into the gathering twilight.

in the twilight of your career, life, etc.

Twilight is used with these nouns:
zone