Bitternut

Bitternuts are items used in the Trouble Brewing minigame. Players can obtain the nuts from the bitternut trees found within the minigame on Mos Le'Harmless using monkeys, which are caught in the same area.

According to Varrock Museum, monkeys on both Karamja and Mos Le'Harmless are very fond of bitternuts, although the nuts can only be found by players on Mos Le'Harmless.