Ricardo Diaz was seemingly killed in Arrow at the hands of an unknown assailant, but it's possible that fans haven't seen the last of The Dragon. It's already been speculated that the main villains of Arrow season 7 are a group from the comics known as the Ninth Circle - and that good be very good news for Diaz.
During the episode, Diggle finally told Oliver and Felicity the truth about ARGUS bringing back the Ghost Initiative with Diaz as a member. Oliver agreed to assist Diggle with capturing Dante, (Adrian Paul from Highlander). The plan was thwarted by Diaz; Dante was warned of the setup and escaped, although Diaz was apprehended by Diggle and Felicity. At the end of the episode, Diaz was in his cell when someone set him on fire. His body was so badly burned that it became easy to believe that Diaz had been killed off. However, it may not be that simple.
Diaz's "death" could be tied to the Ninth Circle, an international crime syndicate introduced in Green Arrow: Rebirth #1 in 2016. Dante's organization functions as a bank that funds atrocities that take place all over the world. Arrow season 7 has already dropped a number of hints alluding to the Ninth Circle that tie directly into Diaz's supposed death.
In the comics, their leader is Dante and one of their members is named Virgil. Like Dante, Virgil shares his name with a character encountered in the latest episode of Arrow. What makes the comparison between Dante's organization in Arrow and the Ninth Circle in the comics even more interesting is the Ninth Circle's method of initiation for their members; people are inducted into the Ninth Circle by "burning" their skin. The reason for this is for them to be reborn as "The Burned". The Burned are a squad of brainwashed soldiers who fight in the service of the Ninth Circle.
Diaz was well aware of what would happen to him if he crossed Dante, which is why he turned on ARGUS. He may also have known that he'd be rewarded if he helped Dante escape; if it wasn't for Diaz, there's a good chance Dante would currently be in ARGUS custody. Even without the Ninth Circle knowledge, it's not hard to conclude that Diaz's decision could have earned him a place in Dante's organization. And as Diaz was seen burning himself, the connection comes into play.
Whatever the status of Diaz, Dante still has connections to another important character from Oliver's life: Emiko. Dante's brief conversation with Oliver's half-sister at the end of the episode revealed that the two secretly knew each other and may have concocted a plot for her to earn Oliver's trust. How both Emiko and Diaz fit into Dante's plans remains to be seen.