Fast, annoying little buggers.
That would be Familiars. I swear to god, I always end up killing more of them than whatever else I'm supposed to be killing on the map.
lemme guess thats on the pyramids 
Mm, it has been there.
But, see, in the server I play, lots of monsters spawn in lots of places. So I've had to deal with them alot. =/
Another monster I find annoying is the Banshee. That stupid scream.
And you can always tell if Shinobi/Aliot is dead, because it will drop stuffz, y'know? But, then again, if you are fighting alot of monsters, you may just turn around to attack the next one and get knifed in the back. D: