The Hallow



The Hallow is an end-game surface biome which is spawned only in hardmode. It has a easily recognizable turquoise-colored grass, multicolored trees, and a huge rainbow in the background. It is the only biome where you'll find Unicorns, Pixies and Gastropods. The Underground Hallow biome can be found directly under a naturally-generated Hallow biome.

The most important property of the Hallow is that it does not exist in a newly-generated world. It only appears when entering hardmode, which is done by defeating the Wall of Flesh. Then, one (maybe more ?) Hallow biome along with a large Underground Hallow biome are generated. The Hallow can also be artificially created by planting Hallowed Seeds in dirt.

The second important point about the Hallow is that it's the only environment through which the Corruption can't spread at all (the opposite also seems to be true). Consequently, its role is very important in hardmode, where the corruption becomes nearly unstoppable. The Dryad will tell the player the percentage of Hallow and Corruption in the world.

Although activating hardmode requires the player to have good equipment, the Hallow is a challenging biome, especially at night, since it's the home of powerful mobs. Don't be fooled by the cute and childish scenery.

Pre-hardmode
If, before defeating the Wall of Flesh, you plant Hallowed Seeds in the ground, then Hallowed grass will appear, and will spread. This is the only way to have a Hallow biome during pre-hardmode.

However it will spread the same way as pre-hardmode Corruption: slowly, on the surface, and only through dirt and grass. It still prevents the Corruption from spreading. Furthermore, Hallow-specific mobs won't appear, since they were only designed for hardmode.

Hardmode
In hardmode, the Hallow extends much quicker. It spreads through dirt, grass, stone and sand (which respectively become pearlstone and pearlsand).

However, unlike hardmode Corruption, it does not spread through mud and clay, therefore there can't be hallowed jungle.

The Hallow will also stop spreading once it has encountered Corruption.

Hallowed Desert


When the Hallow spreads through desert, it becomes Hallowed Desert. It is very similar to the Hallow: the music theme is the same, the mobs are the same (except the Light Mummy), and the background is slightly different.

The sand is replaced by pearlsand. Although their color is different, cacti still drop cactus when cut, and waterleaves are also able to grow.