Its been around since the early days of Magic it was first introduced in Alpha and officially keyworded in 6 th Edition
List of Mutate Cards Archipelagore Auspicious Starrix Boneyard Lurker Brokkos, Apex of Forever Cavern Whisperer Chittering Harvester Cloudpiercer Cubwarden Dirge Bat Dreamtail Heron Essence Symbiote Everquill Phoenix Gemrazer Glowstone Recluse Huntmaster Liger Illuna, Apex of Wishes Insatiable Hemophage Lore Drakkis Majestic Auricorn Migratory Greathorn Mindleecher Mysterious Egg Necropanther Nethroi, Apex of Death Otrimi, the Ever-Playful Parcelbeast Pollywog Symbiote Porcuparrot Pouncing Shoreshark Regal Leosaur Sawtusk Demolisher Sea-Dasher Octopus Snapdax, Apex of the Hunt Souvenir Snatcher Trumpeting Gnarr Vadrok, Apex of Thunder Vulpikeet Zagoth Mamba The Best Mutate Cards #5
And, of course, you might have awesome new sleeves you want to outfit a deck with
Legendary Creature - Dragon Draw (CTRL to add secondary) Land Path of Ancestry This land enters tapped
Colossal Majesty Garruk's Uprising : Whenever a creature with power 4 or greater enters the battlefield under your control draw a card
While the banning of White Plume Adventurer has seen the card dropping right off in Legacy again, the Initiative/Monarch Package is so good that any format where it can be played is a format for Palace Jailer to succeed (namely Duel Commander and Canlander now, though)
