While the collection typically retails for on storefronts like Humble Bundle and GOG, there are legitimate ways to "download" it for free or at no additional cost:
A standalone adventure following Billie Lurk on a mission to pull off the ultimate assassination. Can You Get It for Free? Dishonored: Complete Collection Free Download
Dishonored: Complete Collection —How to Get the Ultimate Stealth Bundle While the collection typically retails for on storefronts
The Dishonored: Complete Collection brings together every major release and expansion in the series developed by Arkane Studios: What is Included in the Complete Collection
While "free download" links on third-party sites are often risky, there are several legitimate ways to get these games for free or at a massive discount through trusted platforms. What is Included in the Complete Collection?
Use trackers like GG.deals to see the current lowest prices across all authorized retailers. A Warning on "Free Download" Sites