Witch's cat

The Witch's cat is used in the Underground Pass quest. It must be recovered from the maze of walkways deep inside the dungeon west of West Ardougne and then used as a distraction to allow the player to enter the witch's house there and search a chest to find a stat restore potion, a super attack potion, a book on the history of iban and a doll of iban.

You can take the cat out of the area by grabbing another one and keeping it with you. When dropping it though, it will always run away, essentially disappearing.

Dialogue
Wearing an Catspeak amulet and talking to the Witch’s cat after Underground Pass is complete results in:

Witch's cat: Thou has slain Iban, most wonderous creation of Kardia, mine mistress! Flee these caves, wretched human, ‘ere her wrath both blaze forth upon thee full mightily!

Player: Bah! Like I’d want to hang around this place?

Or

Witch's cat: Zamorakus mortem tuum erit! (Latin for 'Zamorak will kill you!' ???)

Or

Witch's cat: In nomine Zamoraki, ite! (Latin for 'In the name of Zamorak, go!' ???)

It is to be assumed that there is different dialogue before the completion of Underground Pass.

Trivia

 * The examine text "Curiosity has yet to kill this one..." refers to the idiom "Curiosity killed the cat".
 * If you try and pick up another cat while you already have one in your inventory, you get the message: "It's not very nice to stuff a cat into a satchel...Two is just plain cruel!"