Plunderseeds are seeds of an unnatural plant created by the magic of Discord many years ago, during his chaotic reign over Equestria.
The seeds were created by Discord for use against Princess Celestia, Princess Luna, and the Tree of Harmony. Due to the Tree of Harmony's magic, the seeds did not work as Discord had planned, taking over a thousand years to sprout - long after he had been defeated and supposedly reformed.
The seeds grow into thorny plants which seem to feed off powerful magic, such as the one emitted by the Tree of Harmony, to grow at an unnatural rate. Their purpose is likely to leave all the pony races completely helpless for the pleasure of Discord.
Types and powers
The plants grown from Plunderseeds come in different varieties. The most basic variety seems to be huge, black, thorny vines. They can actively attack ponies in their vicinity, usually trying to entangle them. Those vines are exceptionally powerful and surprisingly resilient, able to render even alicorn princesses totally helpless when wrapped - probably by means of their magic-stealing ability.
A subset exists of more agile vines with heads resembling Venus flytraps. They are able to emit clouds of paralyzing spores which managed to incapacitate Princess Twilight.
The vines can also somehow infest the sky, generating black spiky stormclouds. Those weather formations cannot be controlled by pegasi and are actively hostile to ponies, unleashing lightning bolts upon anything in their vicinity.
The invasion of the vines also causes the day and night to become conflated, which is probably due to the incapacitation of the princesses.
The growths are unable to resist the full power of the Tree of Harmony with Elements restored. They are completely destroyed in the episode Princess Twilight Sparkle - Part 2 within a minute of the Tree regaining its full power, due to Twilight returning the Elements of Harmony to the tree.
- The Plunderseeds can be considered as the main antagonist's in the Season 4 Premiere. Technically Discord was behind them, but he had planted them many centuries ago, back when he was still a full-fledged villain.
- The ones that attack Twilight in the forest resemble facehuggers from the Alien series. One jumps at Twilight in a similar way.