Since we already knew that Katie Cassidy would be back as Black Siren in the final episodes of the season, it seemed likely that Oliver would be allying with some baddies to beat Prometheus.
Amell’s “Desperate times call for desperate measures” points toward Oliver being so beaten down by Prometheus that he’ll even turn to Slade.
Unfortunately, The CW hasn’t announced any details about how, why, or when Manu Bennett might be back as Deathstroke, but we can make a few guesses based on Stephen Amell’s tweet.
Co-showrunner Wendy Mericle recently revealed that Oliver is going to need to deal with some very surprising characters in his battle against Prometheus in the Season 5 finale.