The Witcher, Fallout devs headhunted for Horizon: Zero Dawn

Guerrilla Games sought open-world RPG experts to help it build Horizon: Zero Dawn.

Horizon: Zero World is an open world RPG, which isn't something the Killzone developer had a great deal of experience with prior to kicking off this exciting new IP.

Speaking to gamesradar, studio art director Jan Bart Van Beek and lead producer Lambert Muller said the biggest challenge for Guerrilla was transitioning from hour long stages to experiences which could last "dozens" of hours, packed with multiple possible activities.

Guerrilla resolved this problem by making hires who already had experience on open world projects, notably Fallout and The Witcher series.

The full article linked above includes discussion of how these new hires helped shape the new project by preventing costly mistakes.

Horizon: Zero Dawn is a PS4 exclusive coming in 2016. It was revealed during Sony's E3 2015 conference, and has been one of the highlights of the show.