[quote=@Rtron]
<Snipped quote by Hael>

Monsters return every night year round. When the sun rises, they have to flee. 

For an entire week once a year, the sun doesn't reach Galbar, due to Vestec's eternal darkness. The monsters have free reign for 168 straight hours.
[/quote]

How dangerous are they? Can they be easily fended off?

I'm just trying to ensure that humanity survives that nightly torture.