Annan was very clear.
From the beginning, the Curse Binding was aimed at manipulating emotions.
If he wasn't mistaken, this Curse Binding wasn't the one he and Dmitry had summoned back then.
Instead, it directly entered the "real Curse Binding" through nightmares!
This, in principle, was not difficult.
Although Annan had lost his memory, the Curse Binding hadn't.
It surely knew how it had responded to the summoning back then, how it imposed a severe curse on Dmitry under Annan's cunning plan; it would also know… Bella would remember this duel painfully well.
As long as Bella died, her nightmare would probably be this scenario.
If Annan could predict that he would enter this nightmare one day and leave a message in this nightmare.
The Curse Binding could certainly guess that Annan would enter this nightmare.
It also manipulated this history… possibly setting a simple trap, maybe a mechanism to test Annan, or even just a mark to contact its true body.
