Deep One Rising
Just want to clarify that from the reading of the FAQ, I believe Doppleganger can have the triggered effect of Deep One Rising when played but can the "Forced Response" of Deep One Rising be triggered when using the ability of Hydra which state "Action: Pay 2 to choose a Deep One character in your discard pile and put it into play" and the effect of Twilight Gate which said " Action: Choose a non-Ancient One character card attached to one of your domains as a resource. Put that card into play under your control. If that character is still in play at the end of the phase, attach it to any of your domains as a resource."
Performance Artist
Can Performance Artist be sacrificed to cancel the effect of location card like Shadowed Reef in order to make Deep One lose the benefit of gaining a Terror Icon and give me the opportunity to use some Hastur's events or character to make my opponent's Deep One insane.