If you absolutely cannot go online to activate, you need a scene release. These are and may contain malware. Use only trusted sources (e.g., archive.org user uploads with many downloads/ratings).
For a truly "offline" version (one that doesn't require a downloader to fetch files from Blizzard's servers), users often turn to Internet Archive (archive.org) or community repositories like PCGamingWiki . starcraft 1.18 offline installer
: The ability to toggle between Windowed and Windowed Fullscreen using Observer Mode If you absolutely cannot go online to activate,
Reliving the Legend: How to Get the StarCraft 1.18 Offline Installer starcraft 1.18 offline installer
And two extras. For luck. For the off chance that someone, somewhere, still remembered what a strategy game felt like.