Pet rocks are pets that can be obtained from Askeladden during and after The Fremennik Trials. In the quest, it is used to make Lalli, a troll, give you some golden wool. A pet rock, cabbage, onion, and a potato are the ingredients for making rock soup to please the troll.
Unlike most pets, Pet rocks do not follow the player when dropped, and do not require feeding. However, like Eek the Spider, the rock can be wielded, but it can not be used to fight. Pet rocks do not need to be fed, as they are never hungry, but there is an option to feed it on the "interact" menu nevertheless. Pet rocks can also be talked to, and right clicking and choosing the "interact" option allows you to stroke and perform tricks, such as playing fetch and teaching it the "stay" command.
Like most other pets, pet rocks can be placed in Player-owned houseMenageries. When in a menagerie, players can experience several unique "conversations" with their rock. In addition this, if you drop a pet rock anywhere else in the house (or use it on a cat basket), it will persist even when the house is exited, but unlike when placed in the menagerie, it will merely have an option to pick it up, and no options to talk to it.
For 1,000 Loyalty points, players can buy the option to change the colour of their Pet Rock. After it has been bought, the Pet Rock can then be used on Xuan in Burthorpe/Varrock, Dilwyn in Prifddinas, or Wafa in Menaphos. to change the colour. The colours are red, green, blue, and yellow. This cannot be refunded, but once bought, players can change the colours of their rock as many times as they like. When the Members Loyalty Programme was released, the price had been put on sale for 100 Loyalty Points temporarily.