The game was developed by the same team behind Pac-Man Championship Edition DX, headed by director Tadashi Iguchi and producer Toshiko Tamura.

The team focused heavily on high-score battles as a callback to video game tournaments from the early 1980s, and to appeal towards both veterans and newcomers to the Galaxian series.

Most formations feature large, orbular ships that explode when shot, which can be used to cause chain reactions and easily wipe out larger enemies.

[1][6] Destroying circular Black Hole Bombs sucks in all on-screen enemies, who join the player's side and provide additional firepower.

[1][7][6] After completing work on Pac-Man Championship Edition DX (2010), Namco Bandai Games director Tadashi Iguchi began drafting plans for a sequel to one of his previous projects, Galaga Legions (2008).

While the game sold well and was received favorably by publications,[8][9][10] a common complaint was its drastic departure from the gameplay of the original Galaxian and Galaga,[11][12] both of which were fixed overhead shooters.

[13] The project goal was to create a game that was intuitive and welcoming to both newcomers and franchise veterans, and to find a balance between simplicity and complexity in its gameplay.

[15] Simplicity was a focal point for the project, as the development team didn't wish to create something too easy it lacked difficulty or something too complex it confused players.

Iguchi didn't enjoy the first game's progression for having only one specific way to clear stage formations, believing the new non-linear structure allowed for variations within each level to accommodate different playstyles: "We want it to be both intuitive and flexible.

[14] Among the new design choices for Legions DX was its heavy focus on earning high scores and competing with other players, as the team believed part of the rise in popularity of the shooter genre came from high-score tournaments.

[30] David Wolinsky of GamesRadar+ praised it for being more approachable than to the original Legions, saying that it was much faster and it made the player "feel like a badass" while destroying large waves of enemies.

[30] Carolyn Petit of GameSpot called it "a worthy bearer of the Galaga title", applauding the game's lowered difficulty, graphical style and addictive gameplay.

[5] Daemon Hatfield of IGN praised its graphics and selectable game skins, and for its strategy-based gameplay,[32] while Sammy Barker of Push Square applauded the "fantastic" presentation and its "risk-and-reward" mechanic.

Hatfield was the most critical, saying that the game's content left with little to offer for its price point, expressing disappointment towards its lack of replay value and for bearing little resemblance to the original Galaga.

Barker stated it was not as refined as Pac-Man Championship Edition DX and disliked its large emphasis on pattern memorization, saying that it led to repetition,[33] while Wolinsky criticized the game's lack of extra content.