Yasei no Last Boss ga Arawareta! - Vol. 3 Ch. 14 - Truth Revealed

[Dyrel]

I say Diina is the one who brought the MC's soul / consiousness / mind over to this world placing it into Lufasu's body in the first place.
So Diina would be something like a "goddess" or so.
Or maybe Diina might not be that being itself but something like small part cut off from that being and placed in the world in the role of "Diina" by that being itself.

Either that or she is an evil god who caused the battle / war in that world to begin with.
Like the fight between Lufasu and the 7 heroes being caused by her.

Now that you mentioned it, I feel like she's some sort of a character that act as the system that led the world fate according to the player decision in order to make it actually happen in that world and create a scenario that fits to what the player wishes.

 

[onekele]

Nahhh, the next thing you are going to tell me is that Dina is actually Venus—which is undoubtedly, false.

 

[ChadChampion109]

Dina is the person in login screen on chapter offer MC a role in this fantasy game. The goal or reason why she did that is still unknown