The Underlurker was a massive creature living during the Galactic War on Yavin 4, in the caverns beneath the Temple of Sacrifice. In 3638 BBY a coalition of Republic and Imperial forces used those caverns to reach the Temple and stop Revan from activating the artifact inside it. On their way, they engaged the Underlurker and killed it.
Behind the scenesEdit
The Underlurker appears in the Star Wars: The Old Republic: Shadow of Revan expansion as a boss during "The Temple of Sacrifice" operation.