Palikoi (palikos, singular) are geyser spirits and oversee sacred oaths. According to The Hidden Oracle, the palikoi are twin sons of Zeus and Thaleia. In Percy Jackson's Greek Gods, however, they are the children of Hephaestus and the mountain nymph Etna.

There are currently two palikoi in the forest at Camp Half-Blood called Pete and Paulie. After Meg McCaffrey is taken by the Myrmekes, Pete gives Apollo directions to their nest.