Misstep is an easy restricted include, as is Strip Mine for dealing with things like pesky Tabernacles, Bazaars, you name it
Its S because of its color
This card grants additional red and/or blue mana based on its power at the time you activate its ability
The fact you can make it a Day of Judgment, if you like, is actually pretty useful
The great thing about Be Prepared being a song is you can exert a character to sing it for free, keeping all your ink open to play another character or two into the open board
Opponents didn't even have to show the face-down cards after the game, so an unscrupulous player could technically cast a basic land under the Mask pretending it was a creature to help empty the hand in face of a Black Vise