It's Halloween and Sari introduces the Autobots to Earth's costume-and-candy traditions. However, the entire affair brings up bad memories for Optimus, who is haunted by the ghosts of his past, specifically when he and his fellow cadets, Sentinel Prime and Elita-1, were looking for a crashed Decepticon ship loaded with energon cubes.
- Absentee Actor: Neither Prowl nor Ratchet make an appearance.
- Adult Fear: Imagine being a small child. You meet a stranger that passes herself off as friendly and relatable, only for it to turn out to be a facade she put on so she can steal something from you (or even worse; you). Sari nearly falls for it until Optimus steps in.
- All There in the Manual: Issues #1 & 4 of The Arrival comic mini-series detail how Blackarachnia got to Earth note .
- Body Horror: We see Elita transform into Blackarachnia and hoooooooooo-boy it is not pretty.
- Bittersweet Ending: In the past, Optimus was traumatized by the loss of one of his best friends and strained his friendship with Sentinel, all for a treasure they found but couldn't recover. In the present, Optimus saves his team and Sari from Blackarachnia, but he now knows that Blackarachnia is his fallen friend who refuses to return to the Autobots after everything that's happen.
- Darker and Edgier: Similar in tone to "The Thrill of the Hunt", this episode stands out as one of the darkest stories in the relatively lighthearted Season 1.
- Evil Former Friend: Blackarachnia to Optimus.
- FaceHeel Turn: Elita, after becoming Blackarachnia, eventually joined the Decepticons, having lost her trust in Autobots.
- Halloween Episode: Despite being released in February. Valentine's Day, in fact.
- Hour of Power: Elita's power duplication can only work for a few minutes. This costs her her life (or her life as she knew it, anyway) when she copies Optimus's grappling hook to escape the crumbling cave and her line cuts off right before they can escape.
- Irony: Blackarachnia is certain the Autobots would dissect her, despite having been one of them. The Decepticons might scoff at her organic half, but they at least treat her as one of them.
- My Greatest Failure: Optimus sees the events on Archa-Seven as this, even more so when he learns the true fate of Elita.Bulkhead: So, who was that bug-bot lady?
Optimus: Someone I never should have left behind.
- Mythology Gag:
- Never My Fault:
- Sentinel blames Optimus for Elita's presumed death, despite their trip to the planet being his idea in the first place and that he disregarded the fact that the planet was blacklisted for travel for being dangerous.
- Blackarachnia also blames Optimus for her current state, despite agreeing with Sentinel to search Archa-Seven despite its dangers.
- Not Quite Dead: Elita was thought dead by all concerned, but her mutation masked her energy signature.
- Power Copying: Elita's downloading power. As Blackarachnia, using it on someone causes them to faint. The entire trope is deconstructed, as it shows what would happen if the user attempts to copy something that isn't like them, like say, a giant robot copying a giant spider...
- Start of Darkness: Elita has one after turning into a techno-organic.
- Redemption Rejection: At the end, Optimus offers Blackarachnia to stay and that they could find a way to help her. She rejects it, saying that it'll be long time for her to ever trust an Autobot again, especially Optimus.
- The Reveal: Blackarachnia is Elita-One, having mutated into a techno-organic after attempting to use her powers on the giant spiders.
- They Would Cut You Up: Blackarachnia believes that this would've been her fate had Optimus rescued her and brought her back to Cybertron. Later episodes demonstrate a definite xenophobic streak among other Autobots.
- Trauma Button: Optimus has one when he sees a giant spider as a Halloween decoration, reminding him of the events on Archa-Seven. Sari, unaware of his trauma, assumes he's just a big scaredy cat.
- Wham Line:Optimus: Do I know you?
Blackarachnia: I know how easily you forget your friends, although you managed to remember Sentinel that day!
- What You Are in the Dark: After her Redemption Rejection, Blackarachnia sobs alone on a rooftop. In the Japanese version, she also whispers "Im sorry.", suggesting that she's crying because she wishes she could take Optimus's offer, but can't.
- Would Hurt a Child: Blackarachnia threatens to hurt Sari, doesnt care that using the Key on herself is hurting her and other organics, and throws her off a building in an attempt to distract Optimus.