Direct answer
Download it from the separate Steam demo page. The current listing highlights Act 1, playable Knights, selected annexes, the Demon-linked rewind system, and six interface/subtitle languages.
What the demo includes
The demo introduces the Sovereign's role, lets you manage playable Knights through part of Act 1, opens selected annexes, and demonstrates the Demon-linked rewind system.
Languages
The Steam language table lists English, French, Simplified Chinese, German, Korean, and Japanese for the interface and subtitles. Check the live panel before downloading if a specific localization is essential.
Starting the full game
Treat the demo as a self-contained introduction and start the full game expecting a fresh save unless the current Steam page explicitly offers transfer instructions.
Frequently asked questions
Where can I download the Sovereign Tower demo?
Use the separate Sovereign Tower Demo page on Steam.
Does the demo save carry into the full game?
Plan for a fresh start unless the current Steam page provides transfer instructions.