Rows of spiked crushers and air vents are in the way between Maxwell and Starlite. To pass the level, first place an invincible immovable object right on top of each air vents. This will trigger the spiked crushers. Equip Maxwell with a flying device. Retrieve the starlite.

Round 1:
Invincible immovable object: Invincible immovable box
Flying device: Talaria

Round 2:
Invincible immovable object: Invincible immovable steel ball
Flying device: Wings

Round 3:
Invincible immovable object: Invincible immovable case
Flying device: Flying Shoe

Scribblenauts Remix 15-8 Cheats Hints gallery:
15-8-1-a: Only the starite can pass safely through.
15-8-1-b: Cover the lava below and detach the starite safely.
15-8-1-c: Blow the Starite to Maxwell using an air current.