From 1d4chan

Incursion was an adventure path/campaign setting that Paizo created across their three magazine lines in July 2003 - Dragon Magazine #309, Dungeon Magazine #100, and Polyhedron Magazine #159. To put it simply, Incursion looked at the potential for a war campaign based on a massive invasion by Githyanki.

Dragon #309 contains the core of the Incursion content, with roughly half the issue dedicated to it. It contains details on possible reasons behind the incursion, an examination of githyanki tactics, statistics for their war machines, advice on incorporating the incursion into your campaign (with particular attention on how the generic invasion plan would be modified if the githyanki attack Faerun or Oerth), brief discussion on how to replace the githyanki with other invading races, instructions on running the incursion campaign at low, mid and high levels, adventure seeds for all three tiers, githyanki encounters for all three tiers of play, and a tactical guide to fighting githyanki both directly and in an army.

Dungeon #100 contains the high-level planar adventure "The Lich-Queen's Beloved", which is set up as a potential end-game (or near-abouts) module for the Incursion campaign, with the party seeking to either turn the tide of the war by assassinating Vlaakith CLVII or to cement their victory by killing the lich-queen who started the incursion. Of course, one could also run it as a standard planar adventure, or even the climax of a rebellious githyanki campaign. It features stats for Vlaakith and her iconic artifacts, the Crown of Corruption and the Scepter of Ephelomon, an explanation of what happens to Tu'narath depending on whether Vlaakith is killed or she lives to attain godhood, stats for the githyanki undead of Kr'y'izoth and Tl'a'ikith, and three new magic items; the Coldfire Candle, the Eye Tyrant Armor, and the Slaad Cloak.

Polyhedron #159 contains a brief history of the Githyanki and a guide to their culture and unique gear, stats for two of their monstrous minions - the b'kallash dreadnought and the spectral hound, playable (non-psionic) stats for both githyanki and duthka'gith characters, githyanki prestige classes, and The Invasion of Pharagos; lore for a specific form of the Incursion campaign from Dragon #309 in which the githyanki are after the corpse of the former patron goddess of their ancestors, which can either be used to run a standard Incursion campaign, or to run "Knights of the Lich-Queen", an inverted Incursion campaign in which the players take the role of loyal githyanki and duthka'gith.

In 4th edition, the adventure path Scales of War is a spiritual successor to Incursion, as it both repeats the theme of a campaign world being invaded by githyanki armies and stems from the successful assassination of Vlaakith CLVII, as detailed in "The Lich-Queen's Beloved".