Bik is one of the five Elder Gods, the ancient beings responsible for the creation of the universe, including Gielinor itself. She is the Elder God related to the forest and trees, and is the second youngest Elder God, as well as the second weakest.
The egg from which Bik hatched
After Fate of the Gods, the locations of all the current Elder Gods on Gielinor may be revealed through elder chronicles, which can be found using The Measure. Bik resides underneath Entrana, where her Elder chronicle is found.
In Heart of Stone the player visits Entrana again in search of the place where Bik is resting. Instead, they find a mouthpiece, BikKra, that speaks for the elder god. Upon arrival, BikKra challenges the player with three level 35 BikKra's attendants. After defeating all three, they may then speak with BikKra.
Bik (right) creating Gielinor with Ful and Jas.