Watch Steven Universe: Heart of the Crystal Gems (2018) : Movie Online. Reeling from new information about Steven’s mom, Rose Quartz, the Crystal Gems feel like they’re falling apart! Ruby and Sapphire are at odds for the first time – what will happen to Garnet? A joyful celebration is interrupted when the final battle comes to Beach City – can Steven lead the Crystal Gems to victory? Will they have the strength to pull together and show Home-world the true heart of the Crystal Gems?