The Dweller in the Depths

Over on Cybertron, Perceptor is implementing his grand vision of energy supplying: With a giant power core that will triple energon reserves, apparently, and he was so kind to think ahead that if it happens to screw up and start exploding things, a lever in the command tower only needs to be pulled for the core to be thrown into space. Springer finishes up on inserting the core and it's started up, supposedly allowing the Autobots to be self-sufficient for centuries.
 

Naturally, the ever dastardly Quintessons are watching this from their ship and lamenting on how they once ruled Cybertron until the Autobots' ancestors threw them out, and their attempts to reclaim it have failed. One of them brings up the topic of Trans-Organics, the first attempts at creating cybernetic warriors, but in a nutshell, they were crappy, clunky, and one of them that was meant to be a "living energy siphon" ended up going crazy and destroyed one of his creator's faces. However, instead of dismantling them, they merely stored them away deep within Cybertron, and if they could unleash them then the Autobots would be vanquished. And who better to unleash them than the Decepticons!
 

Galvatron and his lackeys are on Chaar, frustrated and unhappy that they're still there and not ruling over Cybertron, and begins smashing some heads. A teleportation beam forms while the Sweeps and Scourge leg it, revealing two Quintessons, who wish to make a deal with the emperor of destruction. Galvatron is still unhappy about being betrayed from a previous experience, but is talked out of it pretty easily by pointing out that the Quintessons all look rather similar.

The Quintessons show him a hologram of the Autobots' power core, and tell him of how it could make the Decepticons the most unstoppable force in the galaxy, but Galvatron is curious what their part of the deal is. The Quintessons merely consider the deal a peace offering between their races to strengthen strained relationships.
 

The Decepticons arrive at where they were told the path to the power core is, down a mine shaft, but they can't even enter without Ultra Magnus and his posse popping by in an attempt to stop them; meanwhile, the Quintessons point out what we all know, that the Decepticons are actually just going down to the Trans-Organics and yadda yadda, so they fly by to Cybertron to watch the events first hand. The Autobots are delayed by being trapped under rubble from a blast of Galvatron's cannon, and ponder to themselves why the villainous transformers chose this particular mine shaft, since it leads nowhere, according to Arcee. We'll see about that!

In no time at all, the Decepticons find a vast cavern room with pulsating sacs in the middle, believing the promise of the power core to be a hoax, so Galvatron blasts some of the sacs and the machine holding them out of frustration. However, as they turn to leave, Scourge is grabbed by some kind of gorilla with tentacles that came from one of the sacs, but that's the least of their problems! The leader of the Sweeps is saved by a blast from his master's cannon, but that only prompts the rest of the beasts to start attacking everyone else, with a cyborg bear embedding a claw in Cyclonus' shoulder.

While Galvatron busies himself with acrobatics and blasting those freaks, Ultra Magnus, Arcee, Kup, Springer and Wreck-Gar arrive outside the sac room, hearing the screams of the Decepticons, and rush inside. This turns out to be an unwise decision, as the beasts all turn their attention to the fresh meat and go after them, allowing the bad guys to blow a hole in the wall and make an exit.

This also turns out to be an unwise decision, as they're not alone! The living energy siphon the Quintessons discussed shows up and starts picking off Scourge and the Sweeps, draining them of their energy and placing their empty shells in it's containment slots, and makes an attempt on Galvatron's life, though he manages to fend it off and retreats back to where they came from. The energy siphon follows them back in and grabs Ultra Magnus in it's energy draining net, but Wreck-Gar frees him from it, only to be drained by another net, as well as one of the fleeing Sweeps.

On a positive note, the Trans-Organic holds no grudge and also saps the energy of the lesser beasts, vaporising the organic parts and leaving the rest. Springer plays the hero by running up to the beast in an attempt to save their Junkion comrade, and actually succeeds in doing so, but things aren't quite as planned.

He's a zombie, y'see.
 

Well, technically, Arcee and Ultra Magnus use the term "energy vampire", as he drains Springer's energy and feeds it back to the siphon, but he moans with his arms stretched out, so that's zombie for me.

Ultra Magnus claims if they could lure it outside they would have more room to fight, though that plan doesn't go anywhere both because it's stupid (the room's pretty huge anyway) and also because Galvatron pops in to blast him and Kup to the ground, and then fire at the ceiling, causing rubble to fall down and trap them.
 

The energy siphon then grabs Arcee in it's net, who sees if transforming helps in any way, but all it does is prevent the creature from sapping any energy; it's leaving that to the approaching zombies. Conveniently, Kup awakes without any rubble on him and transforms, knocking the zombies aside and running over the net, freeing Arcee, only to get caught by the zombies and made into one of them. Lesson learnt: Being a fast-moving car doesn't save you from an attack of slow-moving energy vampires. Ultra Magnus claims there's nothing they can do to save them, so they just leg it through a blasted tunnel and hope that Perceptor can cure them.

After a brief gloating and vengeance-for-my-face session from the Quintessons, we see how Galvatron and his remaining lackeys are coping. They run into the zombies, who are taken down with single shots, but get up again seconds later, apparently drawn to their energy levels, so the emperor of destruction slows them down in the most hilariously bastardly way possible...

He throws the Sweeps to them.

He just grabs them, tells them something that's barely more than "you're just cannon fodder" and throws them in despite their pleas. This is precisely why I think Galvatron is the best upgrade ever.

He holds onto Cyclonus, but the poor guy is trapped by the siphon's net and is left behind while Galvatron saves his own hide.

Ultra Magnus and Arcee find an exit that's rusted shut and try to blow the damn thing up with a couple of missiles, but that only attracts the siphon, which tears through a wall after them. They hide behind another wall, only to find a pissed off Galvatron, who just desires to kill something today, but is thrown to the ground in three seconds and is drained by the siphon along with Ultra Magnus in it's net. Arcee grabs Galvatron's cannon and destroys the net, as well as blasting the creature until it gets sick of this cavern shit and makes an exit through the wall, heading upwards. Arcee and Ultra Magnus head on their way, leaving Galvatron there to be repaired by the Junkions later, oblivious that the zombies are following them.

Back in the command tower, Perceptor is highly perplexed of Cybertron's energy readings, showing something absorbing it like a vast sponge; Ultra Magnus arrives and tells them of the creature the Decepticons unleashed that's also sucking up energy, so Rodimus Prime finally starts talking in this episode and suggests they destroy that thing before Cybertron is sucked dry. The zombies burst in and start that slow march forwards to them, where Perceptor instantly realises they're suffering from a "rare form of energy depletion" and waffles out a bunch of bullshit about forming a chain and sticking his hand in a plug socket that somehow solves the problem.

Dazed and confused, Scourge asks what's going on, but Springer, lacking good manners, tells them to explain it all, so the Decepticons just jump out a window and regroup with Galvatron, who realises that even without getting a power core, their venture wasn't all for waste, what with the Trans-Organic busting through the ground and intending to supply pain. However, it barely gets to do that before feasting on the power core, giving Rodimus the opportunity to waste Perceptor's time and strength by suggesting they blast the power core into space, and they agree with this in a five second discussion. "And don't come back now y'hear!" Wreck-Gar adds.

The Quintessons realise that energy readings are still coming from Cybertron, even though it should've been sucked dry. Before they can think of the precise reason their plan went wrong, the Trans-Organic beast lands on their ship and hilarity ensues. Perceptor gets back-up power to Cybertron until they can build a new power core, and Arcee proclaims her thankfulness for how everyone is still alive and they've got power as well as disposing of the living energy siphon, so things could be worse, like Rodimus making more decisions that involve destruction of his friend's hard work.

I admit that I don't know my Transformers; remembering who Ratchet and Prowl are still eludes me to this day, but just who is this guy?

Galvatron (the Darkstalkers playing one, not the Sweep-killing one) tells me that the Prime look-alike is actually Streetwise, the Protectobot, coloured like him, and in front is Groove with Wheelie's colour scheme.