The “Insidious” franchise did a curious thing: it introduced a character, killed her off, and then kept bringing her back over and over again anyway. That character is Elise Rainier (Lin Shaye), a psychic medium who has the ability to see the dead. Here’s the problem, though: Elise works better as a supporting character, and making her a main player doesn’t really click. This is evident by “Insidious: The Last Key,” the least successful entry in the franchise, which is the most Elise-forward story in the franchise. This film shows us Elise’s backstory and has her dealing with a haunting in her childhood home. Unfortunately, it’s never very scary or interesting. Ultimately, this is the most skippable entry in the series.