All for Nothing: Enoch spends the entire episode trying to find the Ultimate Weapon, but it ends up crumbling into dust at the end because of its age.
Armor-Piercing Question: Ben gives one to Grandpa when the latter tells him to "keep [his] eye on the prize and remember what's important".
Ben/Four Arms: We do remember! Do you?
Bait-and-Switch: Grandpa grabs Ben and narrowly saves the latter from falling to his death down a bottomless pit. He's relieved and it seems like he retains remnants of his former self...except he only saved Ben because he had the Mask of Ah Puch on his belt.
Book Ends: The episode begins with Grandpa having dung beetle stew with his grandkids (much to their disgust), and it ends with him suggesting they have the leftover dish.
Cerebus Syndrome: In-Universe. Grandpa turns incredibly serious and no-nonsense from the moment the Mask of Ah Puch turns up.
Comically Missing the Point: When Ben and Gwen spit out their food upon learning they've been eating dung beetle, Grandpa figures they simply don't like it because it's too spicy.
Continuity Snarl: This episode isn't the first time Stinkfly has flown with someone in tow. But that doesn't stop Stinkfly from complaining to Grandpa that he's not used to flying with passengers.
He could have just meant such a hefty passenger.
Critical Staffing Shortage: In their search for the ultimate weapon, the Forever Knights only send Enoch and two nooks.
Dramatically Missing the Point: When Ben (who has the Mask of Ah Puch on his person) nearly falls to his death, Grandpa catches him. He expresses relief that they almost lost the Mask when one would think he'd be more worried his grandson nearly bit the big one.
Friend-or-Idol Decision: Grandpa finds himself at a crossroads towards the climax, between stopping Enoch from getting the sword and saving his grandchildren(friend) from Ah Puch. He ultimately chooses the latter. It was definitely for the best, since the sword's power(idol)ended up worthless.
Godly Sidestep: Along the way, the two factions do battle with Mayan god Ah Puch, who seemingly has nothing better to do than guard an ancient sword with no real value.
He's Back!: After their adventure ends, Grandpa casually suggests they have a nice dish of the leftover dung beetle stew, especially while it's cold.
I Ate WHAT?!: When Ben and Gwen learn that the dish Grandpa has been serving them is dung beetles, their eyes go wide and they spit it out off-screen.
It's Personal: Enoch quite clearly recognizes the Tennysons and shows Tranquil Fury over how their last encounter left the forever knights "without a Castle".
Maybe Magic, Maybe Mundane: Although the Sword of Ek Chuaj is confirmed to not have any power at all, it still remains unclear if its guardian, Ah Puch, is an actual deity or an alien worshipped as one. Word of God confirms that the Omnitrix could sample Ah Puch's DNA.
Meaningless Villain Victory: Enoch is able to successfully claim the Sword of Ek Chuaj and proclaims his intent to rule the world with it... for all of 10 seconds before the 5,000-year-old blade crumples to dust. To add insult to injury, the pop-up trivia from the enhanced version of the episode reveals that the sword's power was just a myth all along, so even if it hadn't crumbled to dust, it wouldn't have been of much use to Enoch.
Papa Wolf: Subverted for the most part of the episode, while Grandpa is obsessed with the sword. But towards the end, when Ah Puch is attacking Ben and Gwen, Grandpa grapples with the monster, unwilling to see his grandchildren in harm's way.
"Shaggy Dog" Story: The entire episode revolved around getting to the titular "ultimate weapon" before Enoch did. As it turns out, Enoch does reach the sword, but it's so old that it crumbles to dust. Grandpa Max could've been sitting on his hands the entire time, and the outcome still would've been the same.
Skewed Priorities: Enoch still tries to claim what remains of the sword after it crumples to dust, even when the temple collapses around him, rather than cut his losses and escape. That said, future episodes showed that he still survived anyway.
Sudden Name Change: This is the first episode to use the tile of the Forever Knights, with it also being known by the characters even though the group was just called the organization in their last meeting.
Surprisingly Realistic Outcome: Enoch claims the ancient sword said to have the power to wipe out entire civilizations! ...only for it to crumble to dust nearly the instant he claims it. Grandpa laughs "Guess that's what happens when your ultimate weapon is five thousand years old!" Enoch then starts pathetically scooping up the dust.
Took a Level in Jerkass: While Grandpa Max has had his intense moments before, his usually kind and laid-back personality take a backseat when the Mask of Apuch turns up. Since then, he becomes no-nonsense, obsessed and even snippy towards his own grandkids. Gwen even puts it best when he snaps at her while fixing the Rustbucket.
Grandpa Max: This is metric! I said I needed an 8 inch!
Gwen: (Downcast) Sorry, "Grump-pa".
What the Hell, Hero?: Ben and Gwen put up with Grandpa's out-of-character seriousness for the majority of the episode. But the last straw is when Grandpa insists on beating Enoch to the Sword, despite Ben pointing out that Gwen needs to catch her breath from all the excitement. He finally puts Grandpa on the spot for being so obsessed with the sword that he's neglected his grandchildren.
Ben (as Fourarms): Grandpa, I think Gwen needs a second to catch her breath. Max: No can do. Enoch may already have the sword. Ben (as Fourarms): Ever since that alarm went off, that sword has been the only thing on your mind!
Worthless Treasure Twist: After the Tennysons and the Forever Knights spend the majority of the episode searching for and fighting over the Sword of Ek Chuaj, Enoch finally claims the sword and proclaims his intent to Take Over the World... before the blade crumbles to dust, with Max laughing and joking "Guess that's what happens when your ultimate weapon is 5,000 years old!" To add insult to injury, the pop-up trivia of the enhanced episode confirms that the sword's power is a myth all along, despite the mask seemingly being supernatural and the sword being guarded by a supposed Mayan god.
Word of God confirms that the Omnitrix could sample Ah Puch's DNA.