Which developer created the main Arkham trilogy?

Rocksteady Studios created the main Batman: Arkham trilogy: Arkham Asylum, Arkham City, and Arkham Knight.

The London-based developer was founded in December 2004 by Jamie Walker and Sefton Hill, former Argonaut Games staff. Before Batman, it released Urban Chaos: Riot Response in 2006.

Rocksteady began developing Arkham Asylum after presenting its concept for a Batman game to Eidos, which held the Batman license at the time. The game's 2009 success established the series' distinctive mixture of free-flow combat, stealth, detective work, and gadget-based exploration.

Rocksteady then developed Arkham City, released in 2011, and Arkham Knight, released in 2015. Batman: Arkham Origins is the common source of confusion: it belongs to the same franchise but was developed by WB Games Montréal, not Rocksteady.