The King rat is the last surviving rat in the warehouse in southern Varrock after players poison the other rats during the Ratcatchersquest.
It can only be fought by the player's kitten/cat. If the player asks his/her cat to be cautious, the cat will flee when half its life points are left. If not, the cat will fight to its death. Players should be warned that if their cat dies, they have to get a new one from Gertrude.
If players do not own a full-grown cat, it is recommended that they bring a full inventory of fish (raw or cooked) for the fight. He is MUCH stronger than any other rat a kitten can attack, so caution is highly recommended. They can also ask their kittens to fight cautiously so that it runs away if they start to lose over 1/2 of their life points. Players can use food through the hole in the wall to heal their cat.