Proteus
Πρωτεύς
The prophet who, once seized, turns into anything to slip away.
He knows everything, but will say nothing until he is caught.
When Menelaus seized him, he became a lion, a serpent, a leopard, water, a tree in quick succession — and when Menelaus would not let go, he finally gave the answer.
The word protean, "endlessly changing," comes from him.
SourcesHomer, Odyssey