Arkane Studios estimates skilled players will be able to trot briskly through the entirety of Dishonored's core campaign in as little as 12 hours.
"Play-style matters a lot. Very direct players will probably get through the game in 12 or 14 hours," co-creative directors, Harvey Smith and Raphael Colantonio said in a Dishonored Q&A on the Bethesda Blog.
"Explorers who eavesdrop a lot will take twice as long."
Arkane also detailed the use of mana - small amounts will regenerate, but players will need to use a potion called Piero’s Spiritual Remedy to refill after major spells - and said players will have access to the six major active powers and four passive enhancements.
"Plus there are 40 bone charms in the game that grant small supernatural perks. But no one can have all of these things in one playthrough," the pair noted.
Dishonored is due in October on PC, PlayStation 3 and Xbox 360.