To address the issue you're experiencing with Stick War: Legacy where the screen turns black and you are exited from the app, you can follow these steps:

1. Restart Your Device: Begin by fully restarting your iPad. This can clear temporary glitches that may cause apps to crash.

2. Update the App: Ensure that Stick War: Legacy is updated to the latest version. Open the App Store, search for Stick War: Legacy, and check if there's an update available. If there is, proceed to update the app.

3. Check for iOS Updates: Sometimes app compatibility issues arise due to outdated operating systems. Go to Settings > General > Software Update, and install any available updates.

4. Clear App Cache: Although iOS doesn't provide a straightforward method to clear cache, uninstalling and reinstalling the app can help to reset it. To do this, touch and hold the Stick War: Legacy app icon, select "Remove App," then "Delete App." After deletion, reinstall it from the App Store.

5. Adjust Graphics Settings: If the app has settings to lower graphic details, this may solve the issue especially if your device is struggling with processing graphics.

6. Disable Background App Refresh: Go to Settings > General > Background App Refresh and turn it off for Stick War: Legacy. This can sometimes alleviate performance issues.

7. Free Up Storage: Insufficient storage can lead to crashing. Go to Settings > General > iPad Storage to manage and delete unnecessary files or apps.

8. Contact Support: If none of the above steps work, consider reaching out to the game's customer support for further assistance.

For visual guidance, you can refer to video resources that tackle similar issues, such as this how to fix black screen problem - [learn more], or check out solutions shared by other users on forums, for example Stick war 3 keeps crashing - [learn more].