Such an archive might contain:
If you are determined to find a backup copy, avoid generic "free ROMs" sites. Instead, look for:
Never download from pop-up-ridden domains like download-free-games-now.ru. Stick to communities with active moderation. Castlevania-Dominus-Collection.rar
If you have the file and want to inspect it:
Inside the extracted folder, look for:
The "Dominus Collection" is likely a fan-created or archival effort to compile key titles. While exact contents may vary, such collections typically include:
Modern Masterpieces
Bonus Content