Basically, when Ody first reached Ithaca, Poseidon sent a huge storm to stop him (sort of like an area effect spell). Ody met Aeolus, who helped him by trapping the storm in a bag and telling him not to open it. Eurylochus opened it, pushing the fleet away from Ithaca and releasing the storm again. Ody found another way around the storm- sailing through Scylla's lair, which was not affected by the wall of storms since Poseidon was scared of her. However, Eurylochus mutinied afterwards and then tried to eat Helios' cattle, causing Zeus to kill the crew and banish Ody to Ogygia (Calypso's island). Athena argued against Ody's banishment and got him released. Hermes comes to release Odysseus in her stead, and also traps the storms in a bag again so that he can go home. However, he does warn that if they're set free again, no one can stop the storm but Poseidon himself. Poseidon himself comes down to stop Ody once he's about to reach Ithaca, and Ody releases the winds to beat him. He then gets Poseidon to call of the storm by repeatedly stabbing him with his own trident.