Vortex armor - Official Terraria Wiki

Step 1

↑ When a non-boss enemy is targeting a player with negative aggro who is not currently using an item, the game will prevent them from turning to face the player. Therefore, it only works on enemies who must face left or right towards the player to chase them. A general rule of thumb is that it will not work on enemies which rotate 360 degrees to chase the player. For example, it will work on a Wall Creeper while it is grounded, but not while it is crawling on a wall. It will also not work on attacks outside of normal movement, such as the Giant Tortoise's leap.

Step 2

↑ Information taken from the Desktop 1.4.3.6 source code, methods Update() in Terraria.Player.cs and GetWeaponKnockback() in Terraria.Player.cs. There may be inaccuracies, as the current Desktop version is 1.4.4.9. ↑ A tick is a time unit countable by the software. Most of Terraria's updating logic happens every tick. A tick has the length of 1/60th of a second, hence there are 60 ticks in a second and 3600 ticks in a minute. ↑ Information taken from the Desktop 1.4.3.6 source code, method Update() in Terraria.Player.cs. There may be inaccuracies, as the current Desktop version is 1.4.4.9.