Animorphs 54: the Beginning is widely criticized by fans of the series; some going as far as to say that THIS book is the worst of the 64 books written by K.A Applegate and her ghostwriting team. Aside from the fact that the series ended on a cliff-hanger (which is in no way unique to the Animorphs), fans complain about one thing in particular: the mysterious creature know only as "The One", who can, apparently, assimilate creatures into its very form.* What seems to anger fans is that the One seemingly comes out of left field. K.A apparently introduces a completely different threat unrelated to the Yeerks** and the issue is seemingly unresolved.
For more than ten years, fans have made speculations about the identity of this random and enigmatic creature. Here are three popular theories that I've seen on forums, or in Animorphs Fan Fiction.
1) The One is just like the Ellimist and Crayak: a quasi-omnipotent, semi-omniscient creature; perhaps the very same one who expelled Crayak from his galaxy many years before.
2) the One is another disposable piece in the game between the Ellimist and the Crayak, used by the latter to finally bring an end to the Animorphs.
3) the One is the creature who toyed with Jake in Animorphs 41: the Familiar.***
While these theories are all interesting, and perhaps even probable, I have my own theory. Like I've said, fans complain that the One has come out of nowhere. We know very little about it, and it seems like a random way to close off the series with a creature we have never seen before.
But, good fans of the Animorphs, we have. I ask you to return to the Ellimist Chronicles--released between Animorphs 47: the Resistance, and Animorphs 48: the Return.**** You may recall a creature capable of assimilating the consciousness of other beings--a creature named Father.
Some of you may say: "Ah! But the Ellimist defeated Father! That was, after all, Toomin's first step toward becoming the Ellimist." To which I reply, "So what?"
No, really, who's to say that Father was the only one of his species? Or the only one capable of assimilating the consciousness of other creatures? The Crayak achieved his own near omnipotence the same way as the Ellimist--by throwing himself into a black hole. The Ellimist even notes the improbability of this method working twice. So, who's to say that some other creature didn't stumble upon Father's moon and got trapped in its tentacles; thus starting the same process that began before Father was defeated by the Ellimist? Or that Father was the only member of its species? Maybe Father--or the One, as it calls itself now-- found a way to escape its moon? Maybe the Blade Ship Yeerks landed on its moon and got assimilated that way? Mayhaps Father developed a more violent consciousness this way, based on the Yeerk consciousness; one that would have a vendetta against the Animorphs, or even the Ellimist and Crayak? Maybe it has evolved somehow during its long, sponge-life?
At the very least, I think this theory shows that the One--whatever its origins-- did not come out of left field. At least, not entirely. Its method of assimilating creatures has been shown in the Ellimist chronicles through Father. Whether the One and Father are, somehow, related remains to be seen, and I encourage RAFians to debate, and even add their own theories about the One.
My theory has its flaws, of course. Father isn't sentient; it was a sponge attached to its moon, who developed a collective consciousness through assimilation. It is also unlikely that Father's natural state is capable of leaving its moon. And, since its been years since I've read the Ellimist chronicles, I have no idea of whether the Ellimist destroyed Father's physical form or not. If he did, then my theory is more or less shot down.
Still, I encourage debate, and for you lot to add your own theories.
*Very much similar to, as I understand it, the Borg from Star Trek.
**Except for the fact that, apparently, the renegade Yeerks aboard the Blade Ship worship it.
***Although, I think I read somewhere that K.A shot down that theory.
****A good seven or so books before the One makes its strange debut.