The 'Flying Monster Needles' is one of the villains of the Hidden Floor. This "needles" shaped creatures or monsters can be found in the Cold Land stage. There are many monster needles. They attack in large number to swarm it's enemies. 
Flying Monster Needles is a villain of the Hidden Floor. It's strength was unknown since they weren't show much in the story. In fact, Boro can easily fight them, although according to Boro, he can fight them easily only because they looks like "weapons". It might be due to Boro's strong mentality against weapons.