We can imagine few things more terrifying than being trapped in a small room with dozens of dog-sized rats, which makes the Royal Rat Vanguard a royal pain in the ass. To activate the boss, you'll first have to cut through a bunch of the creatures to draw him out. Watch out, as the rat minions can make you bleed.
Once the boss himself joins the fight, he goes down rather quickly; the trick is to not get overwhelmed by the continually spawning minions. Watch our video above for some additional strategies.
For more help be sure to check out our complete Dark Souls 2 Boss guide.