The Hallow

The Hallow is a new "anti-corruption" biome which may be introduced in 1.1. It can be created with Hallowed Seeds and will stop the Corruption from spreading. The biome has light blue grass and colored trees. It also has its own underground biome which might be where pearlstone is located. Biome name was taken from bandcamp page.

Unicorns and Pixies will spawn here.

It is still unclear whether this biome will actually be included, as it hasn't been explicitly confirmed and named, but only shown on screenshots in dev blog.