Barren

Barren planets are tier 1-6 vanilla planets. Their surface is completely lifeless (no trees, no monsters, no crops), but they can have monsters deep underground.

They are considered to be good for building, but are rather boring otherwise.

You might want to visit Tabula Rasa instead - these planets also don't have monsters, but are green and full of plant life.

Variants
Barren planet can have either Barren II or Barren III as its primary biome. They have different blocks.

Vanilla biome called "Barren" (see below) is not used for Barren planet itself, but it can be a subbiome on other planets.