WARNING: The following contains spoilers for Season 5 of The Seven Deadly Sins, now streaming on Netflix.
The Seven Deadly Sins have always been a tight-knit group, acting more like a family than an order of knights. However, Season 5 has revealed a spy for the Demon King within their midst -- none other than Hawk, Meliodas’ loveable business partner. But why would Hawk spy on Meliodas, and when did he begin working for the Demon King?
Hawk has been a staple of The Seven Deadly Sins since the very beginning. Introduced as Meliodas’ talking pig/traveling companion/Captain of the Order of Scraps Disposal, his presence has never really been questioned. However, Season 4 of the anime revealed that Hawk is connected to Purgatory, even becoming a doorway through which Merlin sent Ban to the realm. Season 4 did not explore this connection further, but Season 5 does.
In Episode 2 of Season 5, "A Meeting with The Unknown," Hawk’s origin is finally further expanded upon. Following centuries of searching, Ban was finally able to locate Meliodas’ emotions in Purgatory; however, neither half of the duo had any idea how to escape back to the real world. After aimlessly searching for some time, the dragon and fox sins notice a presence following them.
This presence is revealed to be Wild, a large talking boar bearing a significant resemblance to Hawk. Intrigued by Ban and Meliodas’ mention of another world, Wild offers to guide them to the Demon King, who guards the portal to the real world. Wild then mentions that he is searching for his little brother, Mild, who went missing over eight million years ago after being kidnapped by the Demon King.
After doing some quick math (and taking their resemblance into account), Meliodas concluded that Hawk was Wild’s missing brother. Meliodas explains that the Demon King used to use animals from the real world to spy on him, peering through their eyes to observe his movements, but they tended to die of old age or injury. To find a being capable of surviving at Meliodas’ side, he looked to Purgatory and selected Mild (Hawk) as his candidate.
But this doesn't necessarily mean that Hawk betrayed the Sins to the Demon King. According to Meliodas, this arrangement was not one that Hawk has been aware of, as the Demon King simply looks through his eyes to keep track of his son.
However, this does mean that, since the beginning of The Seven Deadly Sins, the Demon King has been keeping close tabs on the Sins. Thankfully, due to the Demon King being sealed in Purgatory, he could never use this information for anything other than for his personal knowledge. This is why the Commandments could not follow or track Meliodas’ movements despite Hawk being their king’s spy.
Despite appearing to be nothing more than a loveable talking pig, Hawk has been one of the larger pieces in the Holy War between the Demon and Goddess clans. But now that Meliodas is aware of his father’s deception, how will his relationship with Hawk change, and how will he escape his father’s watchful eyes?