You need a copy of Star Wars Legion core set to play this expansion.
The Rebel Alliance is constantly outgunned in their war against the Empire. Since they cannot hope to match the awe-inspiring military production of a galaxy-spanning Empire, the Rebellion has turned to salvage in order to supplement their forces—such as with the AT-RTs. First introduced by the Republic during the Clone War, the All Terrain Recon Transport, or AT-RT, has since been co-opted by the Rebel Alliance to aid their war against the Empire.
The AT-RT Unit Expansion includes a single new AT-RT miniature for you to add to your Rebel army, complete with three different gun attachments that can be attached to your miniature. Along with the AT-RT, you’ll find the associated unit card and an assortment of upgrade cards for you to enhance your AT-RT and other units.