I’ll cut to chase on this one a bit. Fans got our answer to the lingering, cliff hanging question we were left with at the end of the last episode: Is Felicity alive? Blood Debts has definitively answered: Yes! She is! As the Australian trailer for the episode technically spoiled, Felicity came out of her attack alive, but without the use of her legs. If there was any doubt left that she could still be the one in the mysterious grave over which Oliver has been brooding in the season’s framing device, the episode made sure to include Felicity, waiting in the limo as Oliver finally left the grave. That’s one name officially off the list of who could be dead by the end of the season, but no further clues toward who it is.
During the Liang Yu flashback, Baron Reiter discovered that Oliver’s torso tattoo (a spell transferred earlier by John Constantine) glowed when the Baron approached him with the Orb of Horus. It’s hard to say what Reiter knows now that he’s seen the tattoo, but it’s clear from the fact that he spared Oliver’s life that he has a plan to use Oliver for his benefit now.
This episode also saw Lonnie Machin become Anarky (though not technically called that, he was nonetheless that character). This was a departure for the character as the Lonnie of the comics is actually a young child (usually around 12). In Blood Debt, Machin was also hunting Damien Darhk alongside (and eventually at odds with) Team Arrow. Anarky escaped the vigilantes in the end of the episode, so it seems very likely that he will return to fight another day on the series.