7. Tíryntha. This is a Greek accusative form. See the note on áera, 4, 11.
10. Duodecim annós, accusative of duration of time.
11. Eurystheó. The English verb 'serve' is transitive, but servió ('be subject to') is intransitive and takes an indirect object.
14. quae. See the note on line 1. What is the case of quae?
16. Prímum is chiefly used in enumeration, prímó (line 6) in contrasting an action or state with one that follows it.
19. sécum. The preposition cum follows and is joined to the reflexive and personal pronouns, usually also to the relative pronoun.
22. neque enim. See the note on 7, 12.
26. respírandí, the genitive of the gerund. It modifies facultás. The gerund corresponds to the English verbal noun in -ing.
13. 5. Hóc. We might expect haec referring to Hydram, but a demonstrative pronoun is commonly attracted into the gender of the predicate noun (here mónstrum).
cui erant, 'which had,' literally 'to which there were.' This construction is found only with sum. It is called the dative of possession.