Greyson Grayson's Invitation Location (Spoilers)

[Crinkles]

After I'd found 52 cards and all the other invitations, Greyson's still eluded me.

A guide led me to the correct spot, which seemed quite random and made me feel like I must've missed or forgotten any hints that were supposed to lead me there. Instead I'd spent a lot of time trying to figure out a way to his body without disarming the trap, which was kinda fun but ultimately fruitless

Can anyone suggest the reasoning behind the invitation being found where it is, or quote dialogue that points to it?

[Psyringe]

If I remember correctly, Sixpence mentions that Greyson sent him to that safe. So there is a connection, but it's very faint, and the circumstances aren't explained AFAIK.

I spent a lot of time trying to get to Greyson's body as well - trying to cut off the electricity, or find a way back up from the trapdoor, or find a way to be inside the cage while he dies, etc. ;)