they lure odysseus' men into they're traps and never let them go, creating a time illusion and feeding off their souls.
what danger...
Odysseus is forced to put his men in danger in many situations, but specifically does so when they have to pass by Scylla, the sea monster.
She's a danger to Odysseus mainly because she is a distraction and he need to hurry and get home
Scylla and Charybdis are encountered.
The sailors ears were plugged so that they could not hear and Odysseus was lashed to the mast.
The sirens are a danger that Odysseus and his men must pass to return home.
In the Odyssey, the danger posed by the sirens lies in their enchanting song that lures sailors towards them, leading ships to crash on the rocky shores where the sirens reside. Those who listen to their song are unable to resist and often meet a tragic fate. Odysseus devises a plan to navigate safely past the sirens by having his crew plug their ears with beeswax while he himself is tied to the ship's mast to hear their song without being able to steer the ship towards them.
no cause like you said, they weren't fully out of danger yet
The danger they pose to human beings is relatively small, mainly because they don't exist.
Eurylochus tells Odysseus what has happened to the other 22 men. He did not eat the food as he suspected danger, so he was able to avoid the spell and run back to safety.
Circe used poisoned food to turn them into pigs.
To win the war, win the battle, avoid danger, keep up morale.