The phrase "watches of the night" usually refers to the rounds made by a guard. what does the phrase mean in line 1?

The phrase "watches of the night" has long been used since at least the book of common prayer from 1662. The number of hours in a day is usually divided by 3 or 4 and a guard is assigned in each division. The phrase means that the guard is kept awake during the night time. 

Theseus defeated the minotaur. Odysseus didn't. Odysseus met Calypso. Theseus didn't. Odysseus met Polyphemus. Theseus didn't.

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