Helmacron

The Helmacrons were a fungible and egotistical species about one-sixteenth of an inch tall. Their two ships, the Planet Crusher and the Galaxy Blaster, get involved in the underground war on earth between the Animorph team (Cassie, Rachel, Jake, Marco, Tobias, and Ax) and the Yeerks because of their technology that can sense the transformational power of the blue cube and all those who can use it to morph. Yeerks have knowledge of the species' existence even though Andalites do not.

Description
Helmacrons are "fungible," meaning that the living absorbs the minds of the dead members of the species. Their society is based on a hierarchy with the females at the top as leaders and males at the bottom as slaves. Any major leader is killed so that she does not make any bad decisions and so her followers can look up to her. Any disagreement between two or more Helmacrons is satisfied through bloodshed Helmacrons can communicate through either thought-speak, or the spoken cheer "neep."

All male and female Helmacrons have a humanoid torso and four legs. Their heads resemble squashed inverted pyramids with a barbed chin, two marble-like eyes on top, and a sideways insectlike mouthpart. Females have flat heads and fierce mouthparts while males have forward-slanting heads and less horrifying mouthparts. Those who travel to distant planets wear silver one-piece suits with colored collars that identify them with a certain ship. Planet Crusher uniforms have turquoise collars while Galaxy Blaster uniforms have magenta collars.

History
The two ships, the Planet Crusher and Galaxy Blaster, travel to earth in search of universal domination. The Galaxy Blaster locates the power source of transformation power, or blue box, in Cassie’s family water pump to replenish its malfunctioning engines. Cassie mistakes the ship as a toy and donates it to the charity Goodwill. It is only after she finds another ship, the Planet Crusher, on the pump does she and the rest of the Animorphs suspect that they are facing a second alien invasion. The Helmacrons fight the Animorph until the aliens use the blue box to shrink Cassie, Marco, and Tobias to their own size so the Galaxy Blaster could take Cassie and Marco captive. The rest of the Animorphs trap the Planet Crusher in Cassie's barn and take their dead "leader" as hostages to make them tell where the Galaxy Blaster had taken the two missing Animorphs.

Cassie and Marco trick the Helmacrons into believing that Visser Three has the blue box. They meet the Visser traveling to a meeting and wage war until the Visser defeats the ship with a Dracon beam. The two Animorphs onboard escape using fly morphs and the rest of the Animorphs rejoin the two at the Yeerk meeting. The Planet Crusher escapes and takes the box from Ax to shrink the Visser and Rachel. Ax regains possession of the blue box and strikes a deal with the Yeerks. Cassie and Marco unshrink everyone and bargain with the aliens to allow them to power their engines if they would leave earth. The two Animorphs also try to raise a rebellion among the male Helmacrons.

Both of the Helmacron ships play a key role in the Animorphs' war against the Yeerks. First the Yeerks rebuild the Planet Crusher's morphing energy sensors to track down the Animorphs in a helicopter until Cassie helps take it down with her humpback whale morph. The Galaxy Blaster later returns to earth despite their previous deal with the Animorphs. The males have rebelled and split from their female leaders. Both the males and females look for the blue box like last time and use Marco as a hostage to get the box. They both climb into his nose to stop his heart and the rest of the Animorphs shrink their selves and go after the aliens eventually getting them out of Marco’s body. Once again, the Animorph team makes the Helmacrons leave earth.

Behind the scenes
This species first appears in the Animorphs book The Suspicion and they are mentioned the book The Hidden and return in The Journey.