What can the river styx do to you?

Traditionally, the river had two specific "powers". First, the gods swore oaths on the Styx, because drinking from the River would addle them for an entire year, during which time they would be utterly useless. Second, it was believed that bathing in the Styx would make a person invulnerable, but only one account was recorded, that of Achilles, whose mother held him by the heel and dipped him into the river.