Ice Age uncommon. Jump and Flight are two cards from Magic’s earliest days that have seen many variations over the years. Both had the same mana cost despite the fact that Flight was permanent, part of the story being that Jump was a surprise, which helped offset it’s one-shot nature. Updraft added a cantrip draw to the Jump effect, but added a mana as well. By the time Stronghold had arrived, Leap added a card draw to Jump but offered it at the same mana cast as the original!
Planeshift common. This card was part of an experiment to see just how bad creature removal could get before players would stop playing it in Limited formats. Thanks to its instant speed and single colored mana in the cost during a block where color fixing (and splashing) was paramount, this card still saw plenty of play!
Weatherlight set as being the first appearance of the Weatherlight airship, as shown in the art of Downdraft. But the Weatherlight crew storyline actually began as early as Mirage; the ship’s captain, Sisay, was quoted in the flavor text of Cerulean Wyvern and Teremko Griffin, and her Ring appeared in Visions.
Unhinged uncommon. This card was originally designed for the unreleased Unglued 2 set, and features art originally commissioned for that set. The DCI promo version of this card features new art.
Dissension rare. This card, which is getting a lot of attention as is, went through several incarnations during its design. The original version reduced blue and white spells by one colorless mana each, like the current version, but increased green, red, and/or black spells by one each. So, if you wanted to point a Darigaaz’s Charm at this guy, you had to spend 
Dissension uncommon. White and Blue have had abilities like this as enchantments, such as Sandskin or Gaseous Form. But, as an instant ability, they mirror each other. White tends to prevent damage to creatures, and Blue now tends to prevent damage by creatures (in the form of the shrink ability, like Dizzy Spell).
Dissension uncommon. The Trial side actually began DIS design as a card all on its own, before split cards had been added to the set. The concern was that it didn’t do quite enough on its own, so it was a perfect candidate once gold split cards were added to the set, where the added versatility means each side can be slightly less powerful than a full card on its own.
Dissension common. Dissension features some subtle ways in which the enemy Rakdos and Azorius guilds are opposed. In this one, Rakdos is the guild to get cards like Seal of Doom and Seal of Fire, but Azorius gets a flier with protection from enchantments.
