In a word, starvation. First, Eurylochus demands they stop at Thrinacia, where the cattle of the sun god graze. After landing, for an entire month the winds blow in such a fashion to prevent them from leaving. Odysseus leaves the men to pray to the gods and then "down on [his] eyes they poured a sweet, sound sleep" (12.364). While he is asleep, Eurylochus convinces the other men to kill some of the sun god's cattle in other to not starve to death. The whole episode is another variation on the eating and obeying the gods motifs as well as another way in which Homer celebrates the virtue of temperance.
Odysseus is warned by Circe to stay away from the island of Thrinacia and the cattle which live there because they belong to Helios, the Sun God. She states that there are seven herds with fifty cattle in each herd, all which do not give birth and do not die. These cattle are herded by beautiful nymphs who are the daughters of Neaera and Helios. Circe describes this all to Odysseus, insisting:
Now, if you leave these animals unharmed
and focus on your journey home, I think
you may get back to Ithaca, although
you’ll bear misfortunes. But if you harm them,
then I foresee destruction for your ship
and crew. Even if you yourself escape,
you’ll get back home in great distress and late,
after all your comrades have been killed.
Although Odysseus does his best to prevent his men from approaching the cattle, their deep hunger after being stranded by bad winds on the island leads the men to consume some of the cattle while Odysseus is asleep. Enraged, Helios demands justice, and Zeus responds by killing all of the men but Odysseus. Thus, Circe's predictions do come true.