Sakashima the Impostor – Saviors of Kamigawa rare. Kamigawa block was all about legends, both in the sense of "cards that can have only copy in play at a time" and "stories that have achieved mythic status." So in the run-up to the prereleases, the website told the legends behind the Legends. Here's Sakashima the Impostor's story.
Sea Monster – Tenth Edition common. The Tenth Edition version of Sea Monster is one of the few cards to explicitly declare how heavy it is. So now that you know that a 6/6 Serpent is three hundred thousand pounds and that getting +4/+4 requires 100 pounds, you should be able to triangulate the sizes of other cards, right?
Phantom Monster – Limited Edition Alpha uncommon. When Magic started, flavor text was a mix of original material and (as on Phantom Monster) literary quotes. There are still quotes from the real world, but they appear only in core sets. For example, the Magic 2012 card Taste of Blood quotes Bram Stoker's Dracula.
Moss Monster – Eighth Edition common. Eighth Edition marked the tenth anniversary of Magic: The Gathering and it included at least one previously unreprinted card from each previous set. For Legends, that selection was difficult, because all the really sensible cards had already been reprinted. And that's why a 3/6 got the call!
Lord of the Undead – Planeshift rare. When Lord of the Undead was printed, its only creature type was "Lord" and it gave all Zombies +1/+1. Since then, it's been changed to being a Zombie itself, so now it gives "other Zombies" +1/+1. But if you have twoLords of the Undead on the battlefield, they will quite happily give each other the bonus.
Abattoir Ghoul – Innistrad uncommon. Most ghouls just shuffle around mindlessly, eating whatever human flesh they run across. However, the Abattoir Ghoul has kept his job at the slaughterhouse, presumably because he's already surrounded by flesh, obviating the need for all that shuffling.
Liliana of the Veil – Innistrad mythic rare. The Planeswalker Liliana Vess, the ambitious death-mage, has come to Innistrad seeking a demon. She believes that if she can slay it, she'll be one step closer to being free of an infernal bargain and reclaiming her precious soul. Though her purpose here is self-serving, her mission will drive her straight into the heart of Innistrad's mysteries.
Ghoulcaller's Chant – Innistrad common. The necromantically animated corpses of the dead, called "ghouls" or "the unhallowed," shuffle mindlessly in massive hordes, seeking to devour the flesh of the living. The twisted necromancers who raise them are called ghoulcallers, and they crave the power and destruction brought be their shambling minions.
Night Revelers – Innistrad common. Aristocratic, richly cultured, and cruelly hedonistic, vampires comprise Innistrad's only nonhuman civilization. The four major vampire bloodlines, like noble families, control manor houses, courts, and castles. Distributed across the plane, but concentrated in the province of Stensia, vampires hunt humans for the sustenance they require and the thrill they crave: the blood of the living.
Skaab Goliath – Innistrad uncommon. Some alchemists of questionable sanity create undead by suturing together the mongrel flesh of several cadavers and breathing into them a semblance of alchemical life. These stitched abominations, called skaabs, often inspire mobs of torch-bearing villagers to purge their towns of the unnatural beings—and their creators.
Geistcatcher's Rig – Innistrad uncommon. The incorporeal spirits of the dead, called geists, take many forms. They can be harmless, even protective spirits who haunt the living out of a sense of duty, fealty, responsibility, or love. Or they can be specters of revenge and cruelty, appeased only by mortal offerings.
Back from the Brink – Innistrad rare. From the Innistrad FAQ: Although you're paying the card's mana cost, you aren't casting that card. Abilities that reduce the cost to cast a creature spell won't apply, and additional costs to cast that creature can't be paid.
Creepy Doll – Innistrad rare. From the Innistrad FAQ: If the combat damage Creepy Doll deals to a creature is lethal, you'll still flip a coin. If the creature is still on the battlefield (perhaps because it regenerated), it could be destroyed a second time, depending on the coin flip.
Sever the Bloodline – Innistrad rare. From the Innistrad FAQ: A double-faced creature only has the name of the face that's up. For example, if Village Ironsmith is targeted by Sever the Bloodline, Ironfang wouldn't be exiled.
Angelic Overseer – Innistrad mythic rare. From the Innistrad FAQ: If you control a Human, and lethal damage is dealt to Angelic Overseer, that damage will remain marked on it that turn. If later in the turn you no longer control a Human, Angelic Overseer will be destroyed.