Ichor Bullet

Ichor Bullets are Hardmode bullets that inflict the Ichor debuff to enemies, decreasing the enemy's defense by 15 /  20 points, which effectively can increase the damage from the bullet up to an additional 10 hit points from its base value of 13, totaling the effective damage of up to 23. They are the Crimson counterpart to the Corruption's Cursed Bullets.

Tips

 * When fighting bosses, it is advantageous to keep some of this ammo in the ammo slots so you can switch between these and your main ammo to inflict Ichor and increase damage dealt with your main weapon. It is not recommended to use this ammo type as a main, since other types (most notably Crystal Bullets) can inflict significantly more damage with the Ichor debuff applied.
 * The Destroyer, the and all  are immune to the Ichor debuff, making this ammunition mostly useless against them.
 * Ichor Bullets reflected by Mimics in Expert Mode do not inflict the Ichor debuff on the player.
 * The damage increase from Ichor actually changes depending on the difficulty: on Journey/Classic it will increase the effective damage by 10, 15 on Expert, and 20 on Master mode. This is due to how the effectiveness of defense changes with the difficulty, getting stronger as it gets harder. This, however, only applies to PvP, since defense only gains increased effectiveness on players.

History
Balle d'ichor 灵液弹