Why doesn't Eren's Founding Titan ability to control other titans work on Rod Reiss' titan?


In Season 3 Episode 9 of Attack on Titan, Eren tries to use his Founding Titan
powers to control other titans, on Rod Reiss' titan, but he can't. Why doesn't
this work?




I don't think there's a spoiler-free answer to this.

Warning: Spoilers ahead

> You need royal blood to use the Founding Titan's ability, unfortunately Eren
> is not a royal descendant. When Eren first used this ability it was when he
> came in contact with the Smiling Titan (how she had royal blood is another
> spoiler).




I don't think there's a spoiler-free answer to this.

Warning: Spoilers ahead

> You need royal blood to use the Founding Titan's ability, unfortunately Eren
> is not a royal descendant. When Eren first used this ability it was when he
> came in contact with the Smiling Titan (how she had royal blood is another
> spoiler).

