Analysis of Sonnet XCVII: A Superscription

Look in my face; my name is Might-have-been;
I am also called No-more, Too-late, Farewell;
Unto thine ear I hold the dead-sea shell
Cast up thy Life's foam-fretted feet between;
Unto thine eyes the glass where that is seen
Which had Life's form and Love's, but by my spell
Is now a shaken shadow intolerable,
Of ultimate things unuttered the frail screen.
Mark me, how still I am! But should there dart
One moment through thy soul the soft surprise
Of that winged Peace which lulls the breath of sighs
Then shalt thou see me smile, and turn apart
Thy visage to mine ambush at thy heart
Sleepless with cold commemorative eyes.