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Ayeerk pool cave

Kandrona in the TV series

"The Kandrona is a miniature version of the Yeerks' home sun. It emits Kandrona rays, which concentrate in the Yeerk pools. It is what nourishes the Yeerks. That is why the Yeerks must swim in their natural state in the Yeerk pool every three days — they need Kandrona rays."

A Kandrona is an artificial miniature version of the Yeerks' home sun that generates Kandrona rays. The Kandrona was first created by Seerow in order to allow the Yeerks to survive off-world, with the Yeerks later learning to create their own and installing them on various ships, bases, outposts and planets.


"The Kandrona is a device that produces Kandrona particles. See, it's like this little portable version of the Yeerk's own home sun. The Yeerks need Kandrona particles to live, like a human needs vitamins or whatever. The Kandrona particles are beamed from wherever the Kandrona is and concentrated in the Yeerk pool. Once every three days, every Yeerk has to leave his host and go into the pool. They soak up the particles and then they reenter the host body."

On the Yeerk homeworld, the sun beamed its natural Kandrona rays onto the planet. These rays would also be beamed into molten bodies of water on the planet, known as Yeerk pools; within these pools lived a sentient parasitic species known as the Yeerks, blind slug-like creatures who infested other species in order to be able to truly experience the senses. In the 1960s, an Andalite Prince named Seerow visited the Yeerk homeworld and learned of the Yeerks. Shocked to discover they were as sentient and intelligent as the Andalites but feeling pity that they were stuck in their pools and on their planet, Seerow created the Kandrona, an artificial generator that would emit Kandrona rays. This would then allow the Yeerks to survive off-planet should the need arise.

In 1966, a group of Yeerks led by Akdor 1154, who had infested the bodies of local Gedds, stole Andalite ships and fled their homeworld, escaping into the cosmos. They had also brought the portable Kandrona with them, allowing them to survive. The Yeerks then analyzed and studied the Kandrona technology and were able to successfully create large Kandronas, which they installed on their ships to beam Kandrona rays into the pools they constructed.[1] They were also able to recreate the smaller, portable Kandronas.[2]

When the Yeerk Empire infiltrated other planets, they constructed Yeerk pools and installed a large Kandrona that would always be emitting Kandrona rays into the pool.[1][3] However, due to the Yeerks' biological reliance on Kandrona rays, many enemies of the Yeerks, such as the Andalites, aimed to destroy the Kandronas in order starve the Yeerks.[4]

In 1991, Edriss 562 and Essam 293 decided to travel to Earth in order to explore the planet. In order to survive, Edriss stole several portable Kandronas, which they kept on their ship. These portable Kandronas generated enough Kandrona rays to last them for four years, allowing the pair to survive[2] until 1995.[5] However, when the Kandronas were running low, Edriss conceived a plan to allow the Yeerk Empire to stealthily infiltrate Earth and seize the billions of humans living there as future hosts. In exchange, she requisitioned that the Empire send her more portable Kandronas so that she may survive to continue setting up the foundation for their impeding invasion, which they agreed to.[2]

By 1997,[6] the Yeerk Empire successfully constructed a massive underground Yeerk pool complex[3] underneath a city in California.[7] They installed a massive Kandrona on the top of the EGS Tower to beam the necessary Kandrona rays into the Californian pool. This Kandrona was then destroyed by the Animorphs,[8] forcing the Yeerk Empire to shuttle hosts from Earth to the Pool ship in orbit, which contained its own onboard Kandrona.[4] As the Yeerks did not have the adequate logistics to transport everyone, humans whose Yeerks were dying or had died of starvation were then killed by the Yeerks. Not wanting to cause further human casualties, the Animorphs decided not to destroy the replacement Kandrona that was installed in their city shortly after.[4]


In chronological order:


  1. 1.0 1.1 The Hork-Bajir Chronicles
  2. 2.0 2.1 2.2 VISSER
  3. 3.0 3.1 The Invasion
  4. 4.0 4.1 4.2 The Alien
  5. In VISSER, it is revealed that the Yeerk Empire's invasion of Earth began at the same time Edriss 562 became Visser One. The promotion caused Edriss to fake the death of her host, Eva, in order to free up her time. In #1: The Invasion, set in 1997, it is stated that Eva died two years prior, placing the beginning of Earth's invasion in 1995.
  6. The Andalite Chronicles is said to take place 10 years after the 1966 Yeerk exodus of The Hork-Bajir Chronicles and 21 years before Elfangor met the Animorphs. This places it in 1976, meaning the Animorphs met Elfangor in 1997.
  7. The Beginning
  8. The Stranger
Andalite technology Dome Ship | Escafil Device | Hirac delest | Mirrorwave call | Z-space transponder | Morphing | Mag-Hover Truck | Quantum Virus | Shredder | Gleet Bio-Filter | Prion Virus
Yeerk Technology Anti-morphing ray | Dracon beam | Gleet Bio-Filter | Kandrona | Kandrona Rays | Nova-class Empire Ship | Pool ship | Blade ship | Mag-Lev Train | Hunter Robot | Yeerk Pool | Bug fighter
Ketran Technology Explorer | Time Matrix | Mapping Crystal Quadrant 3 | Uninet | Adge
Other Dropshaft | Ixcila | Pemalite crystal | Pemalite ship | Skrit Na Saucer | Hawjabran Colony Ship | Hawjabran Freighter