| Expert Mode-Only Content: This information (or parts of it) applies only to Expert mode and Expert mode worlds.
The Spore Sac is a Hardmode accessory that is obtained from Plantera's Treasure Bag after defeating Plantera in Expert Mode. When equipped, it rapidly spawns multiple spores around the player that will try to attack any nearby enemies. The spores explode on contact, dealing about 400 damage over 1 second and inflict the Poisoned debuff. This has a small Area of Effect, and can hit more than 1 target. If multiple spores attempt to attack one enemy that dies (no matter how) before all of them reach, they will stop and not be destroyed. The spores can freely pass through blocks, and will chase (and damage) enemies behind and through them.
Spores only spawn within 50' of the player (25 tiles), and will fade if the player moves 50' away from them. A maximum of 10 spores will be on screen at any time. Spores will not spawn within 4' of each other (2 tiles), and will only spawn within 5' of a solid surface (liquids or blocks). If there is not a large enough solid surface within 50' of the player to allow the spacing, fewer than 10 spores will spawn. Each spore fades after 20 seconds, and is replaced by a new one, if there is room to spawn.
- The spores spawn around nearby tiles or walls, meaning that if the player is flying or on a platform without any tiles or walls nearby, spores will not appear. It is possible to clump the spores due to this.
- Spores cannot appear in liquids, but can float into liquids.
- Spores seem to "see" only about 30 feet. They do not react to enemies further away.
- Spores are slow, but if the player stands still, the spores will have no trouble intercepting incoming threats. Caution must be exercised while moving however, as the player will leave their protective flock behind, and any threat in front of the player will have a window of opportunity to reach them.
- Spores will not actively intercept destructible projectiles (such as one fired by Dark Casters), but if the projectile hits them it will be destroyed.
- Spores will not home in on critters, but will explode if they hit one.
- Spores can sometimes target Cultists even if they are passive.
- Spores are especially useful when dealing with enemies like Wraith or Angry Trapper, since they will engage the enemies before the enemies can even reach the player. This also becomes useful when exploring "pocket" caves - a player can move close to the wall and let spores deal with enemies inside before entering the cave.
- Spores do not seem to trigger the teleportation effect of Hardmode Dark Casters in the Dungeon, thus being an efficient way of killing them.
- This item is especially good in tight spaces and against enemies that pass through walls, like those found in the Dungeon or Underground Jungle.
- One very handy use of spores is to fend off any minor attacks while building. Enemies will be killed without the player having to switch to combat items.
- This item is useful for designing AFK Farms combined with good armor as the spores will automatically spawn and damage enemies.