From publisher blurb:
DRAGONS. IN. SPACE.
The Legacy Dragonrider takes the popular fantasy RPG class the Dragonrider, and updates it to be Starfinder-Compatible! The might of dragons is still a force to be reckoned with in a science-fantasy setting, and the dragonrider forms mutually-beneficial a bond with dragon ally to allow them to better face off against robots, space troopers, and even starships!
The dragonrider is a martial class with some magic power and, most importantly, a dragon steed beginning at 1st level.