Leera

Leera is a fictional planet in the "Animorphs" series of books. Leera is a mostly aquatic planet, home to the Leerans, a psychic, amphibian race resembling frogs. The planet has only one continent; it was once used by the Leerans to lay their eggs, though Leeran modern technology means that this is no longer necessary.

The Yeerk Empire targeted the planet for invasion, which resulted in a war between the Yeerks, including Leeran-Controllers, and an alliance of free Leerans and the Andalites. The Yeerk side was led by Visser Four. The war focused primarily on the continent.

Visser One attempted to bio-engineer sharks for use on the planet, believing that they would be useful in the watery Leeran environment. Later, the Animorphs wound up accidentally transported into Z-space, and were picked up by an Andalite ship that brought them to Leera. The Animorphs helped the Andalites and Leerans to set off a bomb that helped to win the war, before the same effect that first brought them into space transported them back to Earth.

The Yeerks ultimately lost the Leeran War, resulting in a weaking of their empire. This also resulted in Visser Four returning to Earth and finding the Time Matrix, though this effect was cancelled out by a change in the timeline.