The remains of the door during the day are necessary materials for exchanging advanced skill books, but they are very important in the new edition, so you should collect them more.
Residual effect of Tianmen: 100 pieces can be exchanged for an advanced skill book.
Advanced skill book: strong wind chop, daily fencing, extinguishing skyfire, meteor fire rain, bloodthirsty, summoning animals. So, if you don't have these skill books, don't be afraid, as long as you collect enough fragments of daytime doors, you can exchange them.
Exchange location: Find a mysterious bookseller in the daytime gate security area.
How to get the sundial: I don't know yet. After all, the Heart Edition is not open yet, so Bian Xiao doesn't know how to do it for the time being. Expect the monster to fall or the task to be obtained.