quos ego

Etymology
, the beginning of a verse in Virgil's  (I, 135), where Neptune, the Roman god of the Sea, berates the winds, whom Juno released to start a storm and harass the Trojan hero and protagonist Aeneas, for causing a storm without his approval.

Neptune starts uttering a threat to the disobedient and rebellious winds (ventī [...] quōs ego, literally “you winds [...] whom I...”), but breaks himself off midstream: Iam caelum terramque meō sine nūmine, ventī, miscēre et tantās audētis tollere mōlēs? quōs ego— sed mōtōs praestat compōnere flūctūs.

Now, winds, you dare to embroil the sky and the earth without my approval, and raise up such a mass? You whom I— But it is better to settle the agitated waves.

Virgil's phrase is an example of the figure of speech called aposiopesis.