The Unicorn is a Hardmodeenemy that spawns in The Hallow. It is a very fast adversary and has a rather large amount of health. It can jump approximately seven blocks (14 feet) high and twenty blocks (40 feet) wide. These factors, combined with a high damage output, can make fighting it difficult. It always drops one Unicorn Horn, a valued item.
Tips
Players who recently entered Hardmode should avoid using melee attacks against Unicorns, as they deal a high amount of damage and are highly resistant to knockback.
The Dao of Pow is effective, as it Confuses Unicorns into running away often, which mitigates its frequent charges.
Fighting them in Water slows their movement enough for normal knockback from Swords to be effective.
Ranged-oriented players may need to use Grappling Hooks or Wings to avoid damage from Unicorns.
Digging a two tile-wide hole just big enough to stand in will allow you to attack the Unicorn without being attacked yourself, since the Unicorn is too big to fit through.
Using a Flamarang is very effective, as its strong knockback will allow you to keep it from charging you. In some cases, the unicorn will not be able to move at all when under these attacks.
A fast, big melee weapon will act effectively on a unicorn, often preventing it from damaging the player.
Using the Golden Shower will immobilize the Unicorn, provided it was properly reforged.
Using the Piranha gun can also prevent Multiple unicorns from moving, as it will stunlock them, and home in to any of them that are remaining.