Space Wars. Droid Dog Strike

Harry and Ava are space cadets living aboard Vantia1, a massive space station that was created after a black hole swallowed their home planet. The black hole was the work of an evil scientist, Vellis, who is holding Harry's parents hostage - and now he's invented a new and terrifying Beast, a three-headed droid dog that can dig up the precious element Vellis needs to power his deadly superweapons. Only Harry and Ava can defeat Vellis and rescue everyone from certain doom ...
Book 4 in this gripping series.