Some packs include an additional foil style card which could be in any rarity
The Book and the Stick
Gallery and List of Phyrexian Language Cards Ajani, Sleeper Agent Batterskull Beast Within Blighted Agent Dismember Elesh Norn, Grand Cenobite (Judge promo + Secret Lair) Elesh Norn, Mother of Machines Glistener Elf Inkmoth Nexus Jace, the Perfected Mind Jin-Gitaxias, Core Augur Jin-Gitaxias, Progress Tyrant K'rrik, Son of Yawgmoth Lukka, Bound to Ruin Mental Misstep Nahiri, the Unforgiving Nissa, Ascended Animist Norn's Annex Phyrexian Arena Psychosis Crawler Sheoldred, the Apocalypse Sheoldred, Whispering One Tamiyo, Compleated Sage Urabrask, Heretic Praetor Urabrask the Hidden Vorinclex, Monstrous Raider Vorinclex, Voice of Hunger Vraska, Betrayal's Sting Plains (two versions) Island (two versions) Swamp (three versions) Mountain (two versions) Forest (two versions) What Sets Have Phyrexian Language Cards
It lets you turn dead or weak cards in hand into effects you might want
Mark Rosewater (April 9, 2012)