"Telepathic pitcher plant" was a name given to the largest bioplasmic organism known, encountered by the USS Voyager in 2375. The name was given by Naomi Wildman, based on her recent biology lessons about Earth plant life. It was a space-dwelling lifeform, approximately 2000 km wide, that preyed on starships. The Doctor's scans estimated that the creature was at least 200,000 years old.
It fed by generating a powerful neurogenic field extending several million kilometers. When a ship entered the field, it caused the crew to begin experiencing delusions of what they most wanted, with the organism appearing as the desired thing. For example, a crew seeking a planet to settle on might see an uninhabited world that perfectly met their needs. Thus the crew would set a course straight to it. Although scans showed no signs of sentient thought, suggesting that the creature operated on highly evolved instinct, the creature also showed signs of great intelligence and cunning; not only would the field influence the minds of the crew to accept the illusion, it falsified the ship's sensor readings to support the illusion. However, should one or more crew members not share the particular desire on which the illusion was based, they would be unaffected, and as the ship approached the creature, would become aware of the danger and alter course away. But, in such a case, the creature would manipulate the crew into restraining those members, keeping them from interfering.
When the ship got to the creature, the neurogenic field would be strong enough to render the crew unconscious, their minds firmly trapped in the illusion; even if they were revived by external stimulus, they would remain trapped in the illusion, unable to acknowledge the reality of their situation. The ship would enter the creature's maw and pass into its digestive chamber, where lightning-like bioplasmic discharges from the walls of the chamber would cause the hull to slowly degenerate on a molecular level. The molecules would be absorbed as nutrients. Eventually the ship, and everything and everyone on it, would be broken down and digested.
In 2336 it consumed the Nokaro, a colony ship containing the friends and family of Qatai. Qatai dedicated his entire life to destroying the creature, and gradually became largely immune to its telepathic manipulation, although he was still sometimes susceptible to it.
In 2375 it attempted to consume the USS Voyager. It lured them by creating the illusion that the creature was a wormhole to the Alpha Quadrant. However, three of those on board were not affected. These were Seven of Nine, who was reluctant to return to Earth out of apprehension as to how she would be greeted, Naomi Wildman, who had been born on Voyager and saw the ship as her home, and The Doctor because of his holographic nature. Despite their attempts to warn the rest of the crew of the danger, the creature was able to convince Voyager to take The Doctor offline and knock Seven out by faking transmissions that claimed the wormhole would disrupt The Doctor's holomatrix and Seven's neural transceiver might alert the Borg to the wormholes existence as they passed through a subspace layer they were monitoring. (Naomi's youth meant that she was relatively ignored by the others).
Having regained consciousness inside the creature and recruiting the aid of the currently-trapped Qatai, the three were able to emit bursts of antimatter gas from Voyager's warp core through ships nacelles. This was then detonated by Qatai's tetryon-based weapons, producing an electrolytic reaction and making the two ships taste undesirable to the organism. This forced the creature to 'spit' Voyager and Qatai's ship out. The crew, which had fallen unconscious under the creature's neurogenic sway, subsequently regained consciousness and the situation was explained to them by Seven, The Doctor and Naomi. Voyager later placed a number of beacons to warn other ships of the organism, while Qatai continued his 'quest' to destroy the creature. (VOY: "Bliss")