This deck is entirely focused on Gengar's Creep Show attack, which knocks out the active Pokémon if it has 3 or more damage counters on it. We accomplish this with Mismagius and Radiant Alakazam, supplementing with Spell Tag when necessary or possible. This deck is currently not tested (although when I get the cards for it I will). If you have any suggestions on how to best take advantage of Creep Show in the expanded format, please leave a comment.
You want to start the game by not leading with Radiant Alakazam and going second. If you do, there is Switch, Prime Catcher (will replace a Guzma), and Guzma. Try to get a Mismagius attacking on your first turn (accomplished with Dusk Stone). Then, use Colress to keep refilling your hand and scare the living daylights out of your opponent with Creep Show!
Have fun playing this deck!