The main RuneScape Wiki has an article on: Spice
The Old School RuneScape Wiki also has an article on Spice.

Spice is an item which is used for making curry. It can be used on an uncooked stew to make some uncooked curry. The curry can then be cooked on a range. The spice can be obtained by either purchasing it from the Spice merchant, or by stealing it using the Thieving skill from the spice stall in East Ardougne with level 65 Thieving.

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