The Hallow cannot naturally exist in a pre-Hardmode world. After defeating the Wall of Flesh, two diagonal strips in a "V" formation will infect the world. One side of the world will be Hallow, the other being Corruption/Crimson.
While the Hallow isn't as dangerous as its evil counterparts, it can still be a deceptively difficult biome.
At minimum, you should have the strongest armor sets available in pre-Hardmode.
- Melee players should at least have Molten armor.
- Rangers should use Necro armor, as it provides the best increases to ranged damage.
- For a mage, the strongest armor set consists of the Wizard set with a Wizard Hat, Diamond Robe and Jungle armor
- As a Summoner, Bee armor is the minimum. The Spider armor can be quickly obtained at the beginning of Hardmode.
For Melee users:
- Night's Edge or Breaker Blade; the former has better damage and knockback, while the latter has greater range.
- An Amarok is a very good weapon that can easily be obtained early on. A Hel-Fire is slightly weaker, and it's acquired similarly.
- Dark Lance is a very strong spear that can handle enemies at close range.
For Ranged users:
- Phoenix Blaster, Shotgun or Clockwork Assault Rifle will deal with most enemies.
- A Molten Fury or any Repeater is useful as well.
For Magic users:
- A Flamelash or Flower of Fire are great for single target damage.
- Laser Rifle or Demon Scythe are very useful for crowd control.
- The Spider Staff is the most reliable minion available. Most Prehardmode minions deal too little damage to be effective against the large numbers of enemies in the Hallow.
- Any Emblem dropped by the Wall of Flesh is highly useful in Hardmode.
- Movement accessories, such as Lightning Boots or variants of the Cloud in a Balloon are very useful.
- Wings should definitely be used if obtained.
- The Expert mode exclusive Worm Scarf reduces damage taken.
- Magic Cuffs are pretty useful to quickly recover mana as a Mage.
- It is almost required to have 400 Health and 200 mana.
- A Reaver Shark or Molten Pickaxe is the best prehardmode pickaxe to have around, however, the Reaver Shark is nonviable as of 184.108.40.206.
- A Hook is always useful for exploring.
The Surface Hallow is the only place where Unicorn Horns and Pixie Dust can be obtained, two materials that are useful for recipes, most notably the Greater Healing Potions and Holy Arrows. It can be generated anywhere in the world once in Hardmode, including the natural Corruption/Crimson biomes.
There are only three enemies that can spawn here:
- Pixies are the most common. They have moderate damage and health, and low knockback resistance. While they aren't too big of a threat, be careful to not get overwhelmed by them, especially at night. It rarely drops the Fast Clock or Megaphone when killed.
- A Unicorn is a very fast enemy that has very high health, knockback resistance, and damage. It can easily catch a player off guard, however it can barely jump, which can be exploited by standing above it.
- At night, Gastropods will appear. They are common and have high Health, Defense, and can shoot lasers. Since it's considered a Slime, the Expert mode exclusive Royal Gel will make it completely harmless.
Most of the Hallow's value lies underground, where Crystal Shards and Souls of Light are acquired. These two materials are required for many early Hardmode recipes, hence they should always be collected or farmed for.
Crystal Shards will grow naturally on the Pearlstone blocks, while Souls of Light have a chance to be dropped by any enemy killed within the biome. A good farming spot for the latter is a wide section of a cavern, where all enemies will spawn within one place. The area should also have an enclosed area to hide in when at low health.
Like every other biome in Hardmode, there are stronger enemies added to those in the regular Caverns.
- Illuminant Bat are very threatening. With no Wings or a substantial movement accessory, they should be avoided, as they have higher stats than Giant Bats.
- Chaos Elemental are dangerous when venturing the Underground Hallow: They can easily catch a player off guard with their ability to teleport, and have high health. They don't jump very high however, so they are easier to kill when standing above them. They can easily be seen since they glow in the dark.
- Illuminant Slime are common and easy to deal with. They should only be treated like a slime with higher stats.
- Enchanted Swords are very rare, and they have a chance to inflict Cursed on hit. They move through blocks, and charge towards towards the player. If hit however, they will start spinning, becoming unable to move. This makes them rather easy to deal with.
- Hallowed Mimic are rare, but they should always be avoided until better gear is obtained, as their massive stats and attack patterns make them incredibly hard to kill underground.
- The Hallow spreads in a similar way to the Corruption and Crimson.
- Unlike Corruption/Crimson, NPCs can live in the Hallow without leaving. In fact, it is a good idea to have your base Hallowed, as this will stop the evil biomes from coming towards it.
- The Crystal Serpent is a great weapon that can be very easily obtained at the beginning of Hardmode. It has a 1/200 (0.5%) chance to be obtained from fishing in the Hallow.