The Parasite is an unlockable passive item.
An orange-colored slug/parasite.
A Parasite grows out of Isaac's head.
Makes Isaac's tears split in two when they hit something. Turns tears into a bronze color. Tears are fired from the Parasite, rather than from Isaac's eyes.
Tears only split when they stop. That means with piercing upgrades (i.e. Cupid's Arrow) they won't split on enemies, and with spectral tears, they won't split on obstacles.
- The range of tears after splitting is determined by how far they traveled before splitting. For example, if the original tear traveled half of its max range and then split, the split tear would travel one-fourth of the player's max range (the un-traveled half of the range divided by two).
- Split tears are treated as newly-shot tears, and therefore random effects like the poison shot from Pinky Eye or spectral tears from Push Pin have a chance to proc on split tears even if the originally shot tear did not have the effect. Conversely, a tear that does have a random, modified effect may lose that effect upon splitting. A notable exception to this is that tears affected by A Lump Of Coal will deal the same damage and be the same size as the original tear was when it split.
- With proper spacing, it is possible to have one of the split tears hit the same enemy and, with very large enemies, with both split tears. This can effectively double or triple your damage output.
- If the tears hit an enemy that normally reflects attacks (i.e. a champion Knight or champion Host) the tears will not be reflected and instead, they will safely split sideways.
- You can sometimes 1 shot TNT with the parasite. When you shoot the TNT, newly formed tears made when the original tear hits the TNT can sometimes hit the TNT as well, causing it to blow up.
- Does not work with items that completely replace tears such as Brimstone and Dr. Fetus.
- Tears will no longer split when they hit enemies if the player has Cupid's Arrow. They can still split if they hit a solid object, such as a Rock or a wall.
- The Parasite works well with items that modify tears. The tears generated by the Parasite are treated as "new tears" and therefore share certain effects. For example, the Pinky Eye trinket will add a 10% chance to generate poisonous tears from the parasite's effect. (See the "Notes" section below for more details.)
- The Parasite has massive synergy with homing, particularly that of Sacred Heart. With homing, tears can hit an enemy, split into two more tears, and then hit the same enemy with both split tears. This is consistent with Sacred Heart, due to the improved homing of low shot speed, resulting in effectively triple damage.
- Possible reference to the Manga/Anime Parasyte as it grows from Isaac's head; the same as the aliens in said series.
- The creature on Isaac's head has a similar appearance (and may be a reference) the Parasite from the flash game The Visitor by Zeebarf.
- In the icon, The Parasite is shown with teeth, but when it attaches itself to Isaac, it loses a tooth.
- The Parasite seems to be placed in the tail end of the (pre-expansion) item database and can behave oddly with regards to spawn rate.