- "It's close, but where?"
- ―Tarr Seirr referring to Grievous' footsteps
When the Clone Wars broke out, Sierr was transferred from his homeworld of Cerea to fight alongside Jedi Master Ki-Adi-Mundi. He was selected to be a part of an elite task force sent to destroy a CIS droid factory on Hypori. However, the Republic fleet was blasted out of the sky before they could even land. Only Seirr and five other Jedi managed to survive the crash landing, but they were quickly surrounded by a droid army under the command of General Grievous. After the remaining Jedi took shelter in the wreckage of one of the assault ships, Grievous ordered the droid forces to stop, and personally entered hand-to-hand combat with the trapped Jedi warriors. During the fight, Seirr tried to strike Grievous from behind, but he was grabbed by the cyborg's clawed foot and crushed to death.