Ferris's role has yet to play out. The story is still developing.
That tiny dagger create a dragon from whatever it cuts. The guy explains it in the anime after he turns his arm into a dragon by cutting it. It allows the cut person to wield dragon fire. Since the ground was cut when Ryner threw the dagger it created a dragon but the dragon had no direction since the ground can't think. So other than being incredibly frightening it was "harmless". I imagine it goes away after a certain amount of time. So they just walked over and took up the dagger when everyone else ran off.
When it comes to the comb, the characters were equally surprised that Ryner was able to destroy it. The guy tells his sister to run because Ryner is not a regular Alpha Sigma. In other words Ryner's special even for an Alpha Sigma. I imagine later it will be revealed why he's so special.In other words this isn't failure on the writer's part. This is just another piece to the ever expanding plot.