i dont get it how did cortana save master chief?

Luke Havergal

Go to the western gate, Luke Havergal,

There where the vines cling crimson on the wall,

And in the twilight wait for what will come.

The leaves will whisper there of her, and some,

Like flying words, will strike you as they fall;

But go, and if you listen she will call.

Go the western gate, Luke Havergal

Luke Havergal.

No, there is not a dawn in eastern skies

To rift the fiery night that's in your eyes;

But there, where western glooms are gathering,

The dark will end the dark, if anything:

God slays Himself with every leaf that flies,

And hell is more than half of paradise.

No, there is not a dawn in eastern skies

In eastern skies.

Out of a grave I come to tell you this,

Out of a grave I come to quench the kiss

That flames upon your forehead with a glow

That blinds you to the way that you must go.

Yes, there is yet one way to where she is,

Bitter, but one that faith may never miss.

Out of a grave I come to tell you this

To tell you this.

There is the western gate, Luke Havergal,

There are the crimson leaves upon the wall.

Go, for the winds are tearing them away,

Nor think to riddle the dead words they say,

Nor any more to feel them as they fall;

But go, and if you trust her she will call.

There is the western gate, Luke Havergal

Luke Havergal.

E.A. Robinson