It is tempting to just Google "steam_api.dll download" and drop it in the folder.
Are you running into this error on a setup, or are you trying to play Dishonored on a specialized handheld like a Steam Deck ? dishonored steamapidll is missing
While steam_api.dll is Steam-specific, Dishonored depends on Visual C++ libraries. A corrupted VC++ installation can sometimes trigger cascading DLL errors. It is tempting to just Google "steam_api