You will be required to install the Substratum Theme Engine and have root access OR the Andromeda add-on if you want to apply this theme:

https://play.google.com/store/apps/details?id=projekt.substratum

For rootless theming with Substratum you will have to purchase the Andromeda add-on pack:

https://play.google.com/store/apps/details?id=projekt.andromeda

A bare-bones Black theme for Android Oreo that focuses on nothing more than theming the system. For other apps I recommend using my Fresh Theme (https://play.google.com/store/apps/details?id=baka.sai.theme) which is also available for free!

If you see un-themed/partially themed notifications even after installing the theme please manually reboot the device (recommended) OR clear all your notifications.

System components themed as of now:
• Android system (also themes the Settings app)
• Files (com.android.documentsui)
• Package installer (com.google.android.packageinstaller)
• Phone (com.google.android.dialer)
• Settings (com.android.settings)
• System UI (com.android.systemui)
• more depending on whatever changes there may be on Android O's final release...

Known Issues (as of 12/09/2017):
• [No fix possible for now] Dark app name text when accessing long-press notification menus when using white notification options
• [No fixes possible for now] WhatsApp Uber black/dark notification header texts when using dark notification options

This theme is 100% open-source
• https://github.com/InFlames03/Oreo-Theme

Special thanks to Nicholas Chum for helping me make this theme possible (t.me/nicholaschum)

Contact for support suggestions and whatnot:
• Substratum Telegram: t.me/Substratum
• Telegram Group: t.me/SaiThemes
• Telegram PM: t.me/BakaBakaBaka