Landstriders are creatures within the Dark Crystal' universe. They were domesticated animals that were often used as transportation for the Gelfling because of their high speeds. Maudra Mayrin owned a couple of landstriders and the Royal Guards often used them prior to the Darkening.
Rian and Deet also used one to get to Stonewood faster.
In the original film, the Landstriders were used by Kira and Jen to get to the Castle of the Crystal.