A character like Eobard Thawne couldn't be dead forever, we are talking about the Reverse-Flash, The Flash's ultimate nemesis and it was finally confirmed that Matt Letscher will reprise his role during this second season eleventh episode of The CW show.
But how is it possible ? Thawne disappeared and was erased from existence when Eddie took his own life to save his friends. Time-travelling rules are so complicated that starting to think about it just gave me headaches.
When thinking about the different possibilities surrounding the Reverse-Flash's return, the first option that comes to mind is alternative earths and Earth-2 but EP Andrew Kreisberg gave a really precise explanation about this improbable return:
“Time on our show does not unfold linearly. Sometimes you’ve seen events from one direction and then you start to see them from the other. This Reverse-Flash is not exactly the Reverse-Flash that we saw disintegrate at the end of the year. It’s a Reverse-Flash from an earlier timeline. It’s not the Earth-Two Reverse-Flash, it’s the Reverse-Flash. That is, hands down, one of our best episodes.”
If we followed correctly, this Reverse-Flash is not from Earth-2 but also more importantly, not the one who impersonated Harrison Wells for 15 years and betrayed Barry. This Thawne is a different version, from another timeline that didn't killed Nora Allen.
Instead we'll meet THE Reverse-Flash, the one that obsessively hates Barry Allen and would do everything to destroy him. Thus, I wonder if a new timeline could be created each time a speedster goes back in time and change the future. It would mean that Thawne developed the ability to travel not only through time but also space.
There was still after Thawne's death, a lot of mystery surrounding his motivations and hates of Barry. This was probably voluntarily overshadowed by the writers planning this comeback to deeper explain the backstory of the Reverse-Flash. If you read the comics you probably have an idea about this subject but the writers have surely find a way to change it a bit and surprise us like they always do.
The Flash returns January 20th on The CW.