Ultimate Weapon

Ultimate Weapon is the twenty-first episode of Ben 10.

Plot
Somewhere in Texas, people are working to obtain some oil underground. An earthquake alerts them and they run as the ground breaks up while the tower falls below. The mysterious quake unearths a large tornado of flames, which then reveal to them a mysterious mask, right before their eyes. Meanwhile, in the RV, Grandpa Max, Gwen and Ben are having a meal. Grandpa Max asks them how it tastes. Ben and Gwen seem to like it, but they immediately are turned off after learning that the crunchy bites in it are dung beetles. An alarm then sounds off and one of the cupboards opens to release a monitor that showed the mysterious mask. Max identifies it as the mask of Ah Puch and it's the key to the most destructive weapon ever known in the world, the Sword of Ekchuah. Max continues and says that Ekchuah is the Mayan god of war, and his sword is legend to wipe out a city in one swipe. Ben is excited by his theory. Max explains that the sword is something not to be used for fun, and it can control the fate of all mankind. Gwen and Ben appear to listen and agree with him.

They arrive at the area where the mask was found, and Max tells Ben to transform and sneak in. Ben insists that he would break in instead, but Max seems to be very serious about the situation. Ben asks Gwen why Max is acting this way and she explains that Max is just trying to save the world. So Ben transforms into Grey Matter, and he climbs up the gutter. Gwen agrees that Ben can be a bit annoying at times, but she seems to be worried about what Max said earlier. Max interrupts her and says that they were only kids who don’t understand the problem going on now. Inside the building, Grey Matter arrives through the drain in the bathroom. Gum is stuck on his head, but little does he know that the place was guarded by two attack dogs.

Grey Matter jumps out of the way before they attack him, and he runs out. Outside, Max and Gwen wait for Grey Matter to open up the basement door. When he does, it seems that Max is very impatient. Gwen picks up Grey Matter and asks why he smells like dog slobber. They walk through the basement hallways, and Gwen and Grey Matter continue to be aware of Max's condition. A vault is then at the end of the line, and Grey Matter opens it up. Inside reveals the mask of Ah Puch, and Max finally gets his prize that he wasn't able to obtain for 40 years ago. Footsteps are then heard behind them, and it was Enoch. It seems that he's after the mask. Before the Tennysons and the Forever Knights go into a fight, a security guard comes in just in time to distract them.

Grey Matter jumps onto Enoch’s face to cover up the eye holes in his mask, while Max and Gwen run out to get the mask to safety. Max and Gwen were able to get out, but Grey Matter was almost thrown into a paper shredder. He hangs on for his life, while Enoch and his henchmen go after the mask. Instead of chasing after them, they head the other direction. The security guard then orders the security to lock down the building, to make sure that they don’t head out the building. Grey Matter was able to jump away from the shredder, and Gwen and Max continue to run away. They see an exit, but a guard was there. They tried another way. Before reaching the exit, Enoch was right behind them, and he grabs the mask away from Max. With a hard decision, Max tells Gwen to hold on to his hand, and they were able to get out of the building. Grey Matter manages to get out also, but lands into a dumpster, and reverts to Ben. Max then tells Ben to hurry up, so that they can catch up to Enoch before he gets the sword. Enoch is in his car, and he looks at the mask with amazement. The driver then sees the RV in the side mirror, and Max is inside. Max turns on the aerodynamics for the front bumper, and he accelerates the RV to ram into Enoch’s cae. Ben continues to try and activate the Omnitrix, but Max’s impatience has led him to put the RV in auto-pilot, and heads in back to put on his old Plumbersuit. While Enoch’s men try to attack the RV, Max jumps out to Enoch’s car and takes back the mask. Max sees the mask, but Enoch had a blade to protect it. Max slips off from the top of the car after avoiding getting attacked by the sword, but he manages to get himself back up. The situation is intense, but without Max’s protection, Ben and Gwen are attacked inside the RV, while the henchmen try to go after them. Gwen and Ben however, were able to get one out of the door, and it was shown that they were headed for Mexico. Their excitement was drawn off after learning that the second man was coming from the RV’s top, but Gwen was able to use the fire extinguisher to get him off the RV, and fall off the bridge and into the water. Max continues to attempt with all his power to try and obtain the mask. Learning that the blade is metal, Max was able to use his magnetized pad to hold onto Enoch’s sword, which had gripped on it fairly hard.

With Enoch distracted, Max was able to take back the mask. A truck was heading toward them. Max tells Ben and Gwen to hold on, but without paying attention to the truck, Max turns on the rocket thrusters, which made a great chance for the truck and the RV to collide. Max was able to avoid the truck, but scratched the side of it. Realizing that Enoch is behind them, he releases tire spikes to slow them down. The RV drives away, but Enoch was ready for his counterattack. Max and the kids stop somewhere due to the RV’s breakdown. Max complains that he needs the correct wrench, and Gwen finds that Max has changed completely since they were notified about the mask.

Ben looks through the mask, and the sockets glow, revealing a hologram that mapped the temple of Ekchuah. With no time to spare, Ben transforms to Stinkfly and flies to the temple instead. Max insists for Stinkfly to go faster, but Stinkfly explains that he isn't used to flying with passengers. They arrive at the temple, but it seems that Enoch and his men are already at the site. They try to open the pyramid doors with dynamite, but it seems that the stone doors are strong enough to stay shut. Max and the kids head another way to find a secret entrance to the temple. As Max tries to look for a switch, Ben decides to use the mask to reveal its location. A glowing brick was shown, and it opened up the tomb with success. With the path dark, Max grabs a torch, but the blinding light made Ben fall into a very deep pit.

Gwen and Max were able to save him, but Max cared more for the mask's safety. They head down the wooden platforms, but before Max was able to warn Gwen and Ben of the dangers of the temple, Ben accidentally activates a booby trap. The temple starts to rumble, and begins to release boulders from above, breaking their path from all directions. Max was able to use a grappling hook from his suit to get them to safety. Ben and Gwen were glad to be safe, but Max was already far in front. Gwen and Ben don’t enjoy being around Max anymore. They find the socket where the mask can be placed, but Enoch was there to stop Max before he can do so. He captures the kids, but before Max tries to shoot his men, holding Ben and Gwen hostage, he worries about their safety more, and surrenders. To make sure that Max and the kids don’t get in the way, he throws them into the Pit of Despair, believed to be bottomless. They were doomed and fated to probably never come back. Meanwhile, as Ben falls down the pit, he was able to activate the Omnitrix and transform into Four Arms. Four Arms manages to grab a hold onto the wall, and grab Grandpa Max and Gwen. Enoch places the mask into place, and a flash from the door indicates its opening. There, a large pyramid shrine rests on top the sword of Ekchuah. Four Arms gets back up with Gwen and Max, and Max was in a rush to get the sword. Four Arms tries to let Max remember what was important the most, and they continue on.

Enoch’s men weren't able to obtain the sword, as there was a guardian protecting it. It was Ah Puch, the Mayan god of death and the underworld. The men were having trouble of trying to control Ah Puch, and it was to the Tennyson’s advantage to use the time to try and go for the sword. Gwen and Max try to head up the pyramid, while Four Arms distracts Ah Puch. It was Max and Gwen, about to get the sword. Unfortunately, Enoch was there to stop Max from using his hook to get it. Max was able to kick him down, but Enoch uses Gwen to distract him from getting to the sword. He realizes that Gwen is more important then the sword and comes to her rescue. While Four Arms continues to fight, he notices that Max and Gwen are in danger, so he gives Ah Puch a powerful punch, and heads up to save them, but unfortunately, he reverts to Ben. Max headed back up to try and stop Enoch. Ah Puch awakens again, giving Max a choice to either save Ben and Gwen, or go after Enoch and take the sword, leaving Ben and Gwen in great danger. He sees that they are more important, and heads down and defeats Ah Puch. Enoch pulls out the sword, and he gloats for his achievement in obtaining the ultimate weapon, though it crumbles and Max laughs at the result.

The temple starts to rumble, and Ben, Gwen and Max and the kids head out. Max insists that Enoch should head out, but he's too greedy to even listen to a request that can save his life. Outside, they see the temple fall and Max seems to be interested in the Dung Beetle stew again. Ben and Gwen were happy for Max to be back to normal, but wonder how to get back. Luckily, Max has the knowledge to pilot Enoch’s helicopter and they fly off.

Characters

 * Ben Tennyson
 * Gwen Tennyson
 * Max Tennyson
 * Foreman

Villains

 * The Forever Knights
 * Enoch
 * Forever Knight Soldiers

Neutral

 * Ah Puch (first appearance)

Aliens Used

 * Grey Matter
 * Stinkfly
 * Four Arms

​Errors

 * Stinkfly says that he isn't used to flying with passengers, but in The Big Tick, he was carrying Max and Gwen with no problem, although it did hinder his agility.

Trivia

 * Grey Matter's transformation sequence is revealed for the first time in this episode.
 * It's revealed Max has searched for the Mask of Ah Puch for over 40 years.
 * The enhanced version claimed the so-called power of the sword was just a legend, despite the guardian.