Mistys had two Expedition printings, and both of them have been on a downward trend for the last year
However, these two cards can combo off with cards outside of the Standard format, with Boommobile possibly the least tricky to pull off since it can go off in many different ways
However, rainbow cards that achieve a top Blade Label grade from the likes of Beckett who are notoriously stricter will likely hold or continue to rise in value
Sure, you can flood the board with Sais thopter tokens as an alternative win con, and you can grind out games by sacrificing Witching Well and Thought Monitor to recast them with Emry to keep the card advantage going
These exiled creatures can be yours or your opponents
Rest in Peace does suffer all of the same enchantment-related downsides as Leyline of the Void however, and it wont surprise anyone