Penetrators are massive, armored, snake-like creatures.
Penetrators usually live underground, and if they're underneath a city or a village, certain trouble is around for the citizens. They have the ability to move around very rapidly and can burrow through anything very quickly. They're equipped with sharp teeth and spikes, which they usually use for defense against enemies or to kill their prey. They are usually the length of three to four Heroes laying head-to-toe, although rumors have said that they've reached the length of seven Heroes.
They also have heavily-armored bodies, due to their thin exoskeletons. Heroes have found it easier to kill a Penetrator by melting the thick armor and then blowing apart or crushing the fragile skeleton within. However, few Heroes have actually killed a Penetrator. They are lethal creatures that can jolt their heads forwards at amazing speeds. They can snatch a Hero, lift it in the air, and use its fork-like tail to grasp it tightly as it tears it apart with its steel pincer-like teeth.
Penetrators have not been a major issue to the public until the Brain Attack. During the incident's spread to Makuhero City, it has been said that several Penetrators were infected by Brains, and thereby came to the city to add to the chaos. The Heroes who were out to eliminate the new threat to the city managed to remove the Brains from the creatures, although being dangerous no matter what the case, they were forced to lure them out of the city. In some cases, they had to kill some of them because they began attacking civillians. Several Penetrators also escaped into the subway systems beneath the city, resulting in about twenty Heroes going down there to deal with them. Several of the Heroes were killed during the mission, although a total of four of the creatures were killed.
Following the Brain Attack, the city of Antropolis declared a state of emergency situation as a horde of strange creatures began raiding the city from beneath the streets. Various Heroes went beneath the city to deal with the issue before it could get any worse. Upon going underground, many Penetrators began attacking them, as huge caverns had formed because of the creatures. The Heroes battled several Penetrators and may have killed several of them, although they stuck to their true mission of finding the source of the creatures, the Queen. After completing their mission by killing the Queen, the Heroes returned to the surface, with many Penetrators remaining. It is said that they eventually left the area to search for a new home, as the newly-formed caverns beneath the city acted as a disturbance.
Since the mission in Antropolis, there have been no major incidents with Penetrators in any public locations. However, they remain a strong and lethal threat to anyone who interferes with them.