Block

A block is a group of sequential expansion sets with shared mechanics, flavor, and rotation schedule. Blocks have ranged in size from two to four sets and were usually named for the first set they contain. A large expansion led off each block to establish its world and mechanical themes, which were explored further in the block's remaining set or sets, which have varied in size. Most block stories took place on a single plane and linked to the stories of adjacent blocks.

In mid-2018, following the Ixalan block, the block structure was retired in favor of discrete large sets.

Theme
The theme is the concept that gives a block its identity, differentiating it from other Magic expansions. The theme can be either mechanical ("bottom-up"), or flavorful ("top-down").

For example, Odyssey block has a mechanical graveyard focus. The block mechanics, flashback and threshold, incentivize greater use of discard and sacrifice effects. Varying the strength and focus of these mechanics allows R&D to highlight differing gameplay elements, such as creature type or multicolored cards, over time.

The theme can also be a genre or setting, which leads to mechanics designed to evoke a feeling, portray an environment, or otherwise enhance the story. Innistrad block is based on gothic horror, and features a tribal component that pits humans against classic monsters, such as zombies and vampires. It also introduced double-faced cards to evoke the horror tropes of corruption and transformation.

If a block is too focused on one aspect of its theme, it can force players to commit heavily to specific archetypes in deckbuilding. One of the most important parts of designing and developing sets is the creation of cross-block synergies to promote a more complex metagame. Synergies are necessary both for the Standard environment in which a block initially releases, and the new Standard environment created when the next block releases (and the previous block rotates out of Standard).

History
During the game's first two years, prior to the introduction of the block structure, Magic expansions usually had no direct continuity. Alliances, released in 1996, was the first set to borrow the environment and mechanics from a previous set, Ice Age, although it did not immediately follow that set. Despite this, Ice Age and Alliances were later grouped with the intervening, but otherwise unrelated, Homelands to retroactively form Ice Age block.

For much of Magic's history, blocks consisted of three sets. Mirage block, released in 1996 and 1997, was the first block developed for the three-set formula. Its first set, the large expansion Mirage, was released in the Northern Hemisphere's autumn, followed by small sets Visions and Weatherlight in winter and spring. This three-set "large-small-small" pattern was the default arrangement for blocks through Khans of Tarkir block. The three sets of a block, along with a core set, filled the four seasonal product slots that feed into the Standard format. The beginning of a new block in the Northern Hemisphere's autumn coincided with the rotation of all cards from the block, and matching core set, from two years prior.

Some exceptions to that pattern were made, typically to expand the third set in order to advance established block mechanics and have enough original material to avoid feeling stale. Rise of the Eldrazi, Avacyn Restored, and Dragons of Tarkir each match that description. They are large expansions to highlight and provide room for a dramatic reboot in gameplay and tone. Additionally, the second set in Return to Ravnica block, Gatecrash, was made large to allow a new distribution of the ten guilds.

The most substantial break from the typical block structure was Lorwyn–Shadowmoor block, which was divided into two mini-blocks, each with a large and small set. Another significant oddity is Coldsnap, pitched as the "lost set" from Ice Age block, which replaced Homelands in that block upon its release.

Two-Block Paradigm
A redesign of the block structure was announced by Mark Rosewater in 2014 and implemented the following year. Core sets were discontinued, and replaced with an additional expansion, allowing for one per calendar season. Replicating the structure of Lorwyn and Shadowmoor, each year's sets were divided into two blocks, each containing a large set followed by a small set. This new default formula, subject to change for special cases, was known as the "Two Block-Paradigm," and was implemented following the release of the subsequent core set, Magic Origins.

Along with the smaller block size, this new release pattern also promised Standard rotations following each block, such that Standard would contain the three most recent blocks. This increased rotation cadence proved deeply unpopular and was reverted to the traditional annual rotation.

The Two-Block Paradigm also introduced a new draft structure for the latter set in each block, consisting of two booster packs from the second set, and one booster from the first. To accommodate the increased emphasis on the smaller second set, the typical size for a small expansion was increased to 184.

Three-and-One Model
The Two-Block Paradigm rapidly proved problematic. It revealed developmental challenges inherent to small sets, and demonstrated that core sets had served an important purpose in allowing for reprints without regard for the mechanics or setting of the more coherent expansions around them.

As a result, Ixalan block was the final block. Beginning in 2018, a "revamped" core set once again filled the summer slot. The other three seasons would each contain a large, standalone set. These sets might continue the mechanics or story of the preceding set, as was typical within a block, on an individual basis, and the number of consecutive sets set on the same world would vary. This new release structure was called the "Three-and-One Model". It raised the overall number a little (with reprints), but the new card number stayed close to the same. Each set would have basic lands.

List of blocks
The following list details all Magic: The Gathering blocks in chronological order. The year given in parentheses is when the first set in a block was released. For the three-set blocks, the Magic year begins with the "large fall expansion," typically in October, with that block's subsequent sets releasing during February and April of the following year.

With Lorwyn and Shadowmoor, as well as expansions following the introduction of the Two-Block Paradigm, Wizards of the Coast printed two blocks per Magic year. For these, the first block's sets come out in autumn then winter next calendar year, while the second block's sets release that spring and summer. All seasons noted here are those of the Northern Hemisphere.

• Ice Age block (1995)

• Ice Age

• Alliances

• Coldsnap replaced Homelands

• Mirage block (1996)

• Mirage

• Visions

• Weatherlight

• Tempest block (1997)

• Tempest

• Stronghold

• Exodus

• Urza's block (1998)

• Urza's Saga

• Urza's Legacy

• Urza's Destiny

• Masques block (1999)

• Mercadian Masques

• Nemesis

• Prophecy

• Invasion block (2000)

• Invasion

• Planeshift

• Apocalypse

• Odyssey block (2001)

• Odyssey

• Torment

• Judgment

• Onslaught block (2002)

• Onslaught

• Legions

• Scourge

• Mirrodin block (2003)

• Mirrodin

• Darksteel

• Fifth Dawn

• Kamigawa block (2004)

• Champions of Kamigawa

• Betrayers of Kamigawa

• Saviors of Kamigawa

• Ravnica block (2005)

• Ravnica: City of Guilds

• Guildpact

• Dissension

• Time Spiral block (2006)

• Time Spiral

• Planar Chaos

• Future Sight

• Lorwyn block (Autumn 2007)

• Lorwyn

• Morningtide

• Shadowmoor block (Spring 2008)

• Shadowmoor

• Eventide

• Alara block (2008)

• Shards of Alara

• Conflux

• Alara Reborn

• Zendikar block (2009)

• Zendikar

• Worldwake

• Rise of the Eldrazi

• Scars of Mirrodin block (2010)

• Scars of Mirrodin

• Mirrodin Besieged

• New Phyrexia

• Innistrad block (2011)

• Innistrad

• Dark Ascension

• Avacyn Restored

• Return to Ravnica block (2012)

• Return to Ravnica

• Gatecrash

• Dragon's Maze

• Theros block (2013)

• Theros

• Born of the Gods

• Journey into Nyx

• Khans of Tarkir block (2014)

• Khans of Tarkir

• Fate Reforged

• Dragons of Tarkir

• Battle for Zendikar block (Autumn 2015)

• Battle for Zendikar

• Oath of the Gatewatch

• Shadows over Innistrad block (Spring 2016)

• Shadows over Innistrad

• Eldritch Moon

• Kaladesh block (Autumn 2016)

• Kaladesh

• Aether Revolt

• Amonkhet block (Spring 2017)

• Amonkhet

• Hour of Devastation

• Ixalan block (Autumn 2017)

• Ixalan

• Rivals of Ixalan

Unofficial blocks
Although in the 3+1 model blocks no longer existed, the extended stay on Ravnica was unofficially named the Guilds of Ravnica block.
 * Guilds of Ravnica
 * Ravnica Allegiance
 * War of the Spark

In the same vein, two Innistrad sets are to come out only two months apart in the latter part of 2021:
 * Innistrad: Midnight Hunt
 * Innistrad: Crimson Vow