aka my full argument for why Terra is in fact one of the Seven Lights in Kingdom Hearts 3. BRACE YOURSELVES, TL;DR IS COMING
Mickey: Seven guardians of light? Well, for Keyblade wielders, there’s me and Riku and Sora. And my three missing friends, that’s six. Then the seventh would be… […] That means…the thirteen seekers of darkness…
Xehanort: Yes, little king. Perceptive. But Sora and another on your list belong to me now. And that puts you three guardians short. But worry not. All of the pieces are destined to appear. Your seven lights just like my thirteen darknesses, whose final clash will beget the prize I seek…
CAN WE TALK ABOUT THIS VERY IMPORTANT SCENE HERE FOR A SECOND PLEASE
This is what a lot of people have used to argue that Terra is, in fact, one of the Seekers of Darkness, because this line appears to infer that Xehanort has both him and Sora in his possession.
However, I think the exact opposite. I think this line utterly proves that Xehanort does not have him, which means Terra cannot be a Seeker of Darkness. Allow me to tl;dr a little lot:
Mickey just listed out six of the seven known Lights: Sora, Riku, himself, and his “three friends,” which obviously refers to Terra, Ventus, and Aqua, the only wielders that this game goes to great lengths to avoid verbally naming until the very end. Judging by Xehanort’s response here, he confirms these six as being the chosen Lights.
“Sora and another on your list.” Does this automatically refer to Terra? Think about it. Xehanort has Sora. Xehanort is about to possess him in both body and heart to claim him as a vessel. If he has Sora, whom else does he automatically have possession of? Those in his Sora’s heart who are waiting to be revived, including Roxas, Xion, and Ventus. Ventus, who was just listed as another Light. Also keep in mind:
Xigbar knows where Ven is. Both his scene with Zexion in KH2 and his remark to Sora earlier in DDD prove that he knows not only where Ven’s body is, but also where his heart is.
Xemnas knows where Ven’s body is. He spent years trying to find the room it’s in – and considering what we learn in DDD, this was most likely with the intention of using him as an easy vessel.
Besides having literally predicted pretty much everything in the KH storyline, Master Xehanort also knows what Vanitas looks like – or rather, whom he looks like.
In summary, Xehanort would have surely made the connection by now that Ven and Sora are very closely linked – and judging by Xigbar’s remarks, he knows that Ven’s heart is currently inside Sora’s.
What’s this mean? It means Xehanort would know that by possessing Sora, he automatically gets Ven as well. And if Xehanort has Ven’s heart, Ven obviously can’t serve as a Light because he can’t be whole again. Let’s go back to his line:
“But Sora and another on your list belong to me now. And that puts you three guardians short.”
The common argument is that the “another” refers to Terra, with the “three guardians” total meaning Sora, Terra, and the unknown seventh Light that Mickey couldn’t name. But if Xehanort actually had Terra, he should have said “Sora and two others on your list belong to me now. And that puts you four guardians short,” referring to Sora, Terra, the unknown seventh, and Ven. But since he doesn’t, and if we assume that his “two” does mean Sora and Ven, this would mean that not only is Xehanort saying “nope I don’t have Terra,” but he’s also agreeing with Mickey’s initial statement that Terra is one of the Lights.
This isn’t the kind of oversight Xehanort would make, least of all in the game whose entire purpose is to emphasize just how truly, terrifyingly knowledgeable and powerful he really is.
Now, getting back to my original statement, I think this proves Terra isn’t a Darkness presently, but I also think it proves that he will not be one, ever. Remember, Xehanort had his whole plan laid out: 12 vessels carefully chosen over time with Sora as the last-minute thirteenth. That plan was ruined (-insert mad cheering for Lea here-), meaning that his search for a thirteenth vessel in KH3 is an improvisation on his part. If he intended to use Terra as a Darkness, it would not be the thirteenth. He would have already had Terra in line among the first twelve, since at first glance Terra would seem like a legitimate choice given his fate in BBS.
Also remember: DDD tells us that the thirteen Darknesses are made up of people who each possess a piece of Xehanort’s heart. Recall how difficult Terra was for Xehanort to maintain a hold on at the end of BBS – and that was with his whole heart inside of Terra. The likelihood of his being able to maintain control of Terra now, with only 1/13th of his heart, is extremely unlikely, if not an outright plothole should Terra actually turn up as a Darkness. And again, keep in mind that Xehanort is very, very intelligent and he’s not going to waste his time this far into the game. Why bother attempting to reign in a vessel who was so much work before and was able to outmaneuver him and set him back for 13 years?
He won’t. Because as he told Terra directly in BBS, "You are just one of many roads that I might choose to take. Trust me. I made certain of that.” It’s my strong belief that Terra is utterly useless to Xehanort now, much like Riku, and so Xehanort is completely ignoring him at this point – and even going as far as letting Mickey and the others have him (by not going after Terra himself), because if Terra can’t serve the War as a Darkness, he’ll serve it as a Light, which is really all the same in the end as far as Xehanort’s motives are concerned.
AND SINCE WE’RE HERE, I’ll also cover the topic of what a Guardian of Light should be, which further supports Terra as one of them:
What exactly qualifies a person as a Light? Let’s look at the similarities between the six mentioned before. Sora, Riku, Mickey, Terra, Ven, and Aqua – we all know from their respective games that they are each VERY light-oriented in their hearts. Riku struggled for a while, but he eventually overcame his darkness to balance it with his light. Terra also succumbed to darkness, but BBS mentions several times that he has a very strong light in his heart regardless. It’s this light that forces Xehanort to take such a long, roundabout way of doing things to finally possess him in the end. Terra and Riku are virtually the same case, a point stressed all the more in Blank Points. So, overall, I’d say it’s safe to assume that the Seven Lights all have to possess strong lights in their hearts. This is kind of obvious, given the name.
Second, these six have been proven to be very justice-oriented. Sora, Riku, Terra, Ven, Aqua, and Mickey are all the types who would – and do – jump headlong and selflessly into danger for others, oftentimes complete strangers. They take their roles as Keyblade wielders very seriously and understand the kind of responsibility that they carry. So, I would also say that the Lights have to possess noble intentions, a strong sense of justice, and a general adherence to the idea of what is “good” in this universe. Also keep in mind that they play the roles opposite to the Darknesses, so they stand for everything Xehanort’s side doesn’t: lawfulness, order, and the general good.
Thus, if Terra is not one of the Lights, then besides finding the unconfirmed seventh (which, by all appearances, is most likely Kairi) the good guys also need to find another wielder who fits the above description. Of all the wielders we know, past and present, no one else fits all these qualities – except Eraqus, arguably, but even he made one really big screw-up that set him apart from the standards set by the six mentioned above. Roxas sort of comes close, but imo isn’t light-centric enough. Even the Foretellers, despite being generally good people, appear to be flawed in ways that ultimately put their own interests before anything else, unlike the six listed above who constantly put themselves last and fight for others and what they believe is Right.
SO. way too much tl;dr, but to sum it up, please please PLEASE do not just go by the word of all these people (including certain high-profile individuals) who preach “Terra isn’t a Light” and/or “so-and-so is a Light” as fact without any evidence to back it up. This happens a lot, and goes back to how fanbases in general have a terrible habit of accepting fan opinions as fact and then lashing out at canon when it doesn’t happen, which is a sad and frustrating thing to watch.
I’m not saying you should believe everything I’ve said as 100% infallible, but I ask you to consider it, and actually think for yourself, before just going with the biased flow and blind claims that are so prevalent in fandom.