Board Thread:Manga/@comment-5184926-20150716034220/@comment-46105162-20200616113602

I think it was Ymir. Chapter 122 Titled "From you, 2000 years ago", a play on the first chapter's title of "To you, 2000 years from now"

Eren to Ymir; "Is it you who led me all the way here?" "You have been waiting all this time... Since 2000 years ago, for someone."

The title similarities and this quoted text makes me over 90% sure.

Edit, I answered a different question.

Eren was crying because he just finished dreaming all of the events that we have been reading. Just like how Eren was able to convince his father to eat and kill the Fritz family through the power of the Assault titan, Eren sees these memories. And he cries.

This is how Eren Kruger, when saving Eren's father, was able to speak Eren and Mikasa's names, even though they were not even concieved of yet. He was able to see into the memories of the future holders of the Assault Titan.

TL:DR, Eren just dreamed the memories he would one day obtain when he gets the Assault titan, the only titan whose memories can see past AND future. (That we know of)