You can kill this monster at level 20 Slayer. You gain 27 slayer experience after each kill. Bags of salt can be bought from any slayer master store.
Use a bag of salt with a nearly dead rockslug to finish it off.
The slime of evil.
White mystic gloves
Gold Pieces (100-400), Dwarven stout, Earth rune (5-47), Chaos rune (2), Potato seed (4), Onion seed (4), Watermelon seed (2), Cabbage seed (4), Sweetcorn seed (3), Chaos Talisman, Copper ore, Tin ore, Bronze bar, Iron ore, Coal ore, Iron bar, Hammer, Mithril ore, Rune javelin (5)