The humans become Titans through the use of an injected medicine, and the Titan form they take is due to the type of medicine injected. Therefore, it can be deduced Bertolt Hoover got an injection that gave him the gigantic form.

Case evidence is Rod Reiss, who became a Titan that is even bigger than Bertolt after he licked the spilled injection that he was trying to give to Historia.


If so, does that mean Historia Reiss would have become a titan of the same size (or maybe even bigger since she would have been injected with the whole serum unlike Rod Reiss that only licked a bit) as her father?

That would kill Eren and Rod seeing as everyone died when Ross transformed except the ones protected by the hardening ability and Kenny who managed to get out but died short after from injuries as seen in the recent episode.

She wouldn't even be able to eat Eren that way and take his titan shifting power and the coordinate since he would be vaporized by all the heat and burried under the wreckage. So she would stay as a mindless titan.

I don't think Rod would want to die by it too so either he didn't knew it would be that big since the other times the ceremony happened the titan was smaller, or she simply wouldn't become that big (for some unexplainable reason or something that I'm not aware of).

In the same topic, from the manga spoilers that I have seen:

If the mindless titans are in fact Marleyans traitors injected with the titan serum, shouldn't there exist some (during all these years) that would also become extremely bigger than the usual ones and become a threat to the walls?

My best guess is that this was missed out by the story writters, or that it would be explained in the future, or because the plot demanded it, or rule of cool. But I could be wrong.

This source, this one and this Reddit page might be important to the question.


5 Answers 5


The serum, which Rod Reiss wanted to inject Historia with, is definitely a powerful one. Seems like it contained powers like burning things around you (on your command) and turning yourself into a giant Titan form.

Does that mean Historia Reiss would have become a titan of the same size (or maybe even bigger since she would have been injected with the whole serum unlike Rod Reiss that only licked a bit) as her father?

I don't think so. The Rod Reiss titan was abnormal. He wasn't even able to walk properly and was dragging himself on the ground. Rod Reiss licked only a little bit of the serum. If he had injected the whole serum, he would be just like a normal (dumb) but a powerful Titan. We have seen from the beginning that the correct way to turn someone into a Titan is to inject them with the whole serum (Eren's case, Rod Reiss family's case). Rod Reiss also wanted to inject the serum to Historia, but Historia wasted the serum so Rod Reiss had no option but to lick it from the ground.

So if the serum was properly inject to Historia, she wouldn't have become such a huge abnormal Titan. She would've been a normal, a powerful Titan and would've chosen to eat Eren (he was the easy target)

The reddit link you provided also agrees that

Wrongful injection of titan fluid is my theory. He licked it, didn't inject it with a needle.

Let's also take the proof from the anime. When Levi confronted Kenny on the verge of death and asked why he hasn't injected himself with the serum considering the burns and the blood loss, Kenny replies

Yeah, I wonder. If I don't inject it right, I might end up like he did (Rod Reiss), all messed up...

So to summarize all of this, Historia might have had the giant Titan form but not as abnormal as Rod Reiss, she would be a controlled Titan. She would've definitely eaten Eren and taken his powers!


What type of Titan is produced is not random, rather people have the knowledge to make serum to confer certain attributes. For example, Eren's Titan did not have the attribute for hardening until he ate the vial of serum for a hardening type Titan.

Rod Reiss was scared for the future of the Reiss family, and so made a serum for a particularly large and powerful Titan type. In fact, I'd say dangerously large and powerful, probably against any advice he'd gotten from his family, since it was so large it destroyed the chamber under the church. However, if Historia had been the one to use it instead of him, she would probably have been of a slightly different size due to natural variation, and the fact that an individual person's Titan is of variable size depending on factors like how tired they currently are.

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    Reasonable answer but I would like to get something more than natural variation and how tired they are as an explanation. I'm not sure if there's anything to take a different look at or sources (since why I asked) but for now I will leave it open until I get a better answer or if I don't get any for some time. Commented Sep 24, 2018 at 15:29

Firstly, The titan serum that Rod Reis had was a special type, under the trivia section of titan injection, the Wiki talks about the labels on the 3 titan injection vials. According to the Wiki: "Strongest Titan" (サイキョウノキョジン Saikyō no Kyojin?) - The one Rod chose for Historia and which he ended up ingesting". What this means is that the vial that Rod reiss wanted Historia to use was labelled strongest titan. Using that quote as a guide, it makes sense to hypothesize that the serum was specially made to make one of the strongest titans ever. We can all agree that from the effect that the Rod Reiss abnormal had on its surrounding, it makes sense to say that he got some heat related ability that burned whatever he came in contact with. Also, In my opinion, size is a big factor when determining how strong a titan is. Going with those 2 facts, The "strongest titan" serum probably created a very big titan with a heat related ability.

Now to your question, If Historia did get injected with the serum (In the right way, lets think about a perfect case scenario of her becoming a healthy titan), I believe that there could have been 2 possibilities.

Going with my theory of what kinda titan the "strongest titan" serum could create, Historia would have been a titan just as big as the Rod Reiss abnormal but instead she would be able to walk and run like normal titans (while being pretty much stupid and mindless like average titans) and she would have been so big that the place would collapse and then burn from coming in contact with her (I'm trying to be as realistic as possible). PS: a very bad ending cause everyone pretty much dies.

The other possibility is that Rod reiss was very big only because he licked the titan serum instead of injecting it into himself and therefore the little amount of the serum did more harm than good. In this case I'm assuming the "strongest titan" would involve a normal sized titan with heat related abilities. If that were to be the case then when Historia gets injected, she would be the same size as her half sister freida Reiss (be the average titan size), but then she would have an extra ability of burning whatever she touched (she's also mindless like a base titan). At this point I don't know how they would have taken the plot if that were to happen.

But then the fact is, we don't have sufficient information to correctly state how big she would have been but we can guess based on the limited data. I hope this answers your question.

source: http://attackontitan.wikia.com/wiki/Titan_injection (scroll down towards the trivia part to see where the Wiki talks about the labels on the titan serums). Thats what i based this prediction on.


So i will go straight to the point, i thing when rode reiss said " i chose strongest titan for you" i think thats the same titans who made the walls their height is 50 meters each and with hardening they made it up to 60 meter wall. so (so my guess is that serum was taken from these titans ( and people who praise the walls knew about titans being in walls and alsoknew about reis being a titan shifters so they had ways to tak a serum from these titans and just because they are high enough they can outstand even Eren( eren is not a blue blood to control them thats why he is an easy target). so when rod reis licked that serum he had a broken spine thats why the effect of becoming a titan broke on him, we saw that when coni springers whole family became titans and they were given gas to breath thats (all the titans became normal but conis mom didn't because she was already weak with her legs so thats why rod reis could not walk, so i think i made out a pretty good statement on why rod reis said a strong titan


Maybe the serum was taken from a colossal Titan within the wall which is why he grew to be so large and was able to burn things in his immediate vicinity like a colossal titan he is a royal so he would have knowledge of the Titans in the walls and access to them

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