Swift for Samsung is a bedrock theme with over 150 overlays, each with a dark or black option, supporting the Samsung S7, S8 and 8 note, including S8 Oreo.
Make sure your system supports the use of a bedrock theme. See above list supported.
Download the theme Substrate engine application and theme. When you open the substratum application you will find the theme inside.
Supported Android
Download Swift for Samsung Dark Black Substratum Theme 3.8 Patched APK For Android