WARNING: This article may have spoilers for The 100 series finale. Read at your own risk.

The 100 series finale is almost coming on The CW. The episode is titled "The Last War" and it is one of the most powerful installments of the entire run of the series. No one is safe now that the ultimate battle is coming and it remains to be seen whether or not a happy ending is possible.

Despite all the uncertainties, it seems like The 100 series finale will dive back into the past. There would be some cameos and surprise guests coming within this episode. In fact, executive producer Jason Rothenberg, who directed the finale, teased what viewers can expect.

Speaking to TVLine, Rothenberg said that they'll try to wrap as many things as they can since this is the final episode of the entire series. He, then, promised that there are some surprise guests. Fans can expect a lot of big events here, considering that it's the series' last run.

For now, viewers have to wait to see the surprise guests appearing in The 100 series finale. There's a chance that some familiar faces would show up since the story looks back in the past. This is a way for the series to honor its legacy, as well as those who have been part of the show throughout its run.

Also, Rothenberg revealed that the final scene in the penultimate, when Clarke (Eliza Taylor) chose to relieve Madi (Lola Flanery) of her pain, was originally meant to open the series finale. However, the episode was too long, so they had to put the scene at the end of episode 15.

Meanwhile, the promo of The 100 series finale showed that Clarke is in a difficult position. She is doing her best to save the people that she loves. But then, she ended up hurting herself in the process. She wanted peace, yet she recognized that this is something that's not easy to achieve.

Clarke is still dealing with the loss of Madi while looking back to everyone she's lost in the past. There have been a lot of unexpected deaths in the final season and some of the remaining characters may not make it out until the end. For Clarke, it's a long journey for her and she'll do everything to win the last war.

The 100 series finale will be airing on Wednesday, Sep. 30, on The CW.