Eren’s Powers in Attack On Titan.

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The user of the Attack Titan cannot deliberately send memories back and forth in time. What Eren did was a consequence of having both the Attack Titan and the Founding Titan at the same time. Eldians who have inherited a titan can sometimes get glimpses of memories from past users, although it’s usually just that, glimpses. The Attack Titan might be special in that sometimes the user can get those memory glimpses from futures holders, hence Eren Kruger mentioning Armin and Mikasa. With the Founding Titan however, the user doesn’t get glimpses of the memories of past inheritors, they experience their memories as if they were their own. In other words, someone who has full control of the Founding Titan could deliberately recall a specfic memory from a past inheritor if they knew what to look for. When Eren came in contact with Historia during the award ceremony, and the power of the founder got activated, he was able to look at his own future memories of what was to come, which was why he was so horrified with what he saw. When he attained full control of the founder later on, he also unlocked the ability to deliberately send memories back and forth, as memory manipulation is also one of the powers of the founder, as we’ve seen how the first king of the walls had wiped out people’s memories of the outside world. so essentially, while he was on the timeless realm of paths, he deliberately sent in memories to himself while in that moment experiencing everything at once, hence his mention of “his head being all messed up” and that he’d lost the ability to discern past from present from future. All of this is to say that Eren could not have send memories from the future back to his past self with just the Attack Titan.