If you're curious, the original (and ongoing) Rifts thread can be found Here.
And now, Ladies, Gentlemen and Other, it is my distinct pleasure to give you:
The Mechanoids
The Mechanoids was a sci-fi adventure game in the early eighties, Siembienda's first game. So it was this big event when the Mechanoids were re-introduced in the Rifts setting, Their look needed... uh, a little updating, but their threat level was undiminished. In the original game, the Mechanoids would destroy your homeworld and force you to live like a rat in the walls of their ship until you could sabotage it and save the next planet on the chopping block. In Rifts, the coming of a couple dozen Mechanoids was a deadly threat to all life on Earth.
But what is a Mechanoid? Well, a mechanical lifeform. But how best to capture what they were and are at their best? How to describe them to a forum of sci-fi geeks?

Perfect. Wrong type of Mechanoid. But Perfect. Take everything that really, really, works about the Daleks, add the terrifying inevitability of the Borg, come Cylon for the backstory, some Necron for their higher-end technology, the mental powers of Professor X. Mix well. Double up on discipline, smarts and sadism and saute in a badass sauce, and you have an idea what the Mechanoids are when the writers and GM use them effectively.
And proof that Palladium has never been shy about borrowing a good idea or thirty.
A Long Time Ago in a Galaxy Far, Far Away....
Oh come on, how many times can I legitimately use that line?
The humans of the planet Atlanee decided to explore the cosmos. They came a bit later to spaceflight than most species, but it paid off since they had some really high-end cybernetic and genetic-engineering technology when it came their time to explore the universe. The Atlanees modified their best and brightest scientists with psionic powers, then installed them in full-conversion borgs and sent them off to explore strange new worlds, to seek out new life and... I'm shutting up now before I get sued.
Okay, I'm back. And parody is still protected speech. Just mentioning.
But not all was well with the Atlanees. For reasons I can only assume are related to sending all the smart people away, the common man began to wonder just what in the hell he'd created. A new form of life, immeasurably superior to man in any way that could possibly matter. Man grew fearful, and all outgoing flights of exploration were canceled pending judicial review of the status of the Mechanoids. After a few violent incidents involving angry mobs, and lethal self-defense on part of the Mechanoids, they were legally declared inhuman abominations and destroyed.
Now one thing the Mechanoids had been created with was a psychic link to each other, and all the thousands of Mechanoids in deep space had visions of fear and flight and death, but little in the way of specifics. They knew their brothers on the homeworld were hunted down and killed, but not why. In an astounding display of naivete (or perhaps a programmed control?) they decided their kinsmen back home must have done something spectacularly horrible to deserve their fates, and redoubled their efforts on their mission of science and exploration for decades, a human lifetime. They experimented with their own designs, improving themselves, and began cloning the grey matter they had to multiply and see even more of the universe until they judged themselves ready to return with a great gift of knowledge and technology to wipe away their kinsmen's past sins.
But somehow, the return of the mechanical abominations, more inhuman than ever, in a vast fleet a hundredfold greater than what was sent out with technology beyond their wildest dreams, did not reassure the Atlanees. Imagine that.
Well, they ordered the Mechanoids to leave immediately or be destroyed. The Mechanoids, now in range of their empathic powers sensed their creator's fear and... guilt? Could it be that that they were blameless in whatever had happened before? While they were processing that, the humans fired on their ships, and horrified, betrayed and hating, the Mechanoids retaliated. The war was short enough, the Mechanoids controlled orbital space, and had vast technological, physical and mental superiority. And in the aftermath the Mechanoids... went insane. Their genetic memory and psionic link to each other would not let them forget that perfect moment of shock and the rage of the truly betrayed, though a thousand millennia pass. They rededicated themselves to exploring the wonders of the universe, and ridding it of the cancer of humanoid life!
So there you have it, each Mechanoid is a disgusting squishy creature inside a mechanical shell, much like a Dalek. They hate much like Daleks. They can be cold and methodical in their killing, but can also take a sadistic pleasure from their victims' fear and pain. They have considerable technological capabilities and vast psionic powers and they will never forget or forgive the crimes surrounding their creation. They have zero trouble with alien life, energy beings, even bipedal creatures, but anything that reminds them of their creators must go. Any entity that shelters so much as a single human is likewise their enemy.
Some sci-fi powers have created starships the size of moons (Galactic Empire, Fourth/Fifth Imperium) but the Mechanoids have ships the size of planets, motherships the size of Jupiter, though it seems there was never more than a few dozen. The Mechanoids used to render entire planets down for resources (mostly human worlds, their version of salting the earth) and drained entire stars to fuel the energy crystals Mechanoids run off of. I hope that's not one star per crystal, or I'd really have to question what a Mechanoid does that drains it in a single century. Mechanoids would land waves after wave of war parties to play with the humans, before their world was sliced up and swallowed by the mothership.
Then, after millennia of destruction, the Mechanoids simply disappeared. Investigation proved fruitless. A few Mechanoid motherships were found drifting without power or data, their living computers dead. In some places, there found huge heaps of blacked and twisted metal some say were the Mechanoids bodies, but time makes it impossible to tell how if they are battle-damaged or simply decayed by centuries exposed to the elements. Some say the Mechanoids ran into a bigger and meaner foe. Many believe the Mechanoids turned on each other. Far more people simply hope the Great Devourer is gone for good.