Time turner watch - Artie, Pete, Myka, Leena and Claudia travel back in time and save the Warehouse, Jinksy, HG, Mrs. Frederick and Trailer.

That Metronome thing - Claudia was planning to use it for her best friend so the writers should let her.

The Egyptian book of the Living and/or Dead - Let's steal from the Mummy and use some world threatening necromancy.

I think that the stop watch that Artie took from MacPherson's room will make him go back in time to save the Warehouse. Mrs. Frederic, since she is connected to the Warehouse, and died because the Warehouse explode will be revived while the others will stay dead.

I just have to add to this that Trailer is safe, he left the Warehouse with Claudia, so during the explosion, he was with Claudia, Leena and Mrs. Frederic at the B&B.

For the other two, Jinksy & HG, I don't think they might be back. I surely hope they will because Jinksy is Jinksy and I couldn't stop crying after I saw he was dead & HG, I love her to pieces. I ship her with Myka and I want my ship to happen, but still, I don't think they will go back on the show.

Partly because Aaron Ashmore, right now, has a part in another series, Lost Girl & I think he will stay there for a little longer AND Jaime Murray is going back on Hustle. Another thing to add for Jaime Murray is, that she was spotted landing in Toronto the day they started shooting Season 4, and all the fandom thought she was going back as HG BUT after a day she left and we are not sure whether she could have shot a scene or not.