In Dinosaur-centric decks like Gishath, Sun's AvatarGishath, Sun's Avatar, you could use it to fetch up the brand new Ghalta, Stampede TyrantGhalta, Stampede Tyrant to spill your hand full of creatures onto the battlefield, and create an instant army, or grab Etali, Primal ConquerorEtali, Primal Conqueror to get some free spells
People can get caught out when you drop menace on them, so holding Falthis back until the right moment can be a solid play
When activated, Jester's Mask will shuffle the cards in the opponent's hand into their library while giving the player a new hand of cards from their library
Now, how much of that is due to the cards chosen, and how much is down to Lands being altogether less game-warping than say, Enchantments, is another question entirely
Land Color tag templates(None) Color tag templates(None) Sunpetal Grove This land enters tapped unless you control a Forest or a Plains
This means that any and all creatures under a Phenax player's control can be used as a source for milling, with Phenax itself being able to mill seven cards per turn when it's a creature