Heavenly Slime

Desktop/Console/Mobile-Only Content: This information applies only to the Desktop, Console, and Mobile versions of Terraria.

The Heavenly Slime is a Hardmode enemy and a slime variant frequently summoned by Queen Slime alongside Crystal Slimes and Bouncy Slimes. It flies around trying to ram into the player.

Trivia

The Heavenly Slime's gore's sprite is the same as the Fledgling Wings sprite.
The Heavenly Slime, Spiked Slime, Baby Slime, Slimeling, Crystal Slime, Golden Slime, and Bouncy Slime are the only slimes without their own banner.
The Heavenly Slime can be considered a Hallow counterpart to the Slimer, as it looks and behaves similarly. The only differences are that the stats have minor differences, and that the Heavenly Slime does not have a wingless version.

The Bestiary entry for the Heavenly Slime: "Crystal slimes on the purple spectrum grow wings much like their royal creator, becoming aerial threats."