O thou, my lovely boy, who in thy power
Dost hold Time's fickle glass, his sickle hour;
Who hast by waning grown, and therein show'st
Thy lovers withering, as thy sweet self grow'st.
If Nature, sovereign mistress over wrack,
As thou goest onwards still will pluck thee back,
She keeps thee to this purpose, that her skill
May time disgrace and wretched minutes kill.
Yet fear her, O thou minion of her pleasure!
She may detain, but not still keep, her treasure:
Her audit (though delay'd) answered must be,
And her quietus is to render thee.
Unlike the straightforward primary modern meaning of  servant , here “minion” follows  the Early Modern England usages  “darling” or “paramour.” 
 This line echoes the emotional tone of the opening, with another  exclamatory  “O”, reinforced by an exclamation mark at the end of the line.  The urge to “fear her” is panicky. Nature may defer his ageing but this is only to please herself, and his ultimate fate is unchangeable. 
 Unlike previous sonnets where Shakespeare has urged the boy to procreate or where he believes his verses will immortalise the boy, here death is presented as inevitable.
Sonnet 126