A quest walkthrough for Demon Slayer can be found here: www.runescape.wikia.com/wiki/Demon Slayer
Chat with our AI personalities
look on runehq
If this is part of the Demon Slayer quest, then the link below should direct you to your answer.
By doing Demon slayer quest
Talk to Gypsi Aris and she will give you it.
bucket of water