The Soulbound Journal is a Journal tied to the soul of a warlock's patron (to be decided  by you with your DM) allowing you to commune and pass information to them, while they may respond in kind, through the pages of the book, the likelihood depends on your patron.

A leather bound journal that never seems to run out of pages and all past writings other than your own, though quite clear are completely illegible. While seeming very old this book seems quite resilient. 

Notes: Spending a long rest with the journal in your possession., Communication, Social, Utility