Apparently putting a bunch of cursed and evil objects all in one place can have unintended consequences.
Between Annabelle and Annabelle: Creation, we basically got the full story of the titular doll’s backstory, but Annabelle 3 will bring the story forward, showing what happens once the doll comes into the Warrens’ possession.
Once in the artifact room, Annabelle will have an effect on the other cursed objects there.
We’ve also heard that Annabelle will terrorize the Warrens’ daughter Judy and will bring things to life in a horrific, Night at the Museum-type situation.