Please email supportdos@larian.com, with a brief description and a save just before this fight.
Each save is a folder in the '..\Documents\Larian Studios\Divinity Original Sin Enhanced Edition\PlayerProfiles\<ProfileName>\Savegames' folder. In Windows Explorer, right click on the save folder and select 'Send To | Compressed (zipped) Folder' to zip it.
Perhaps also include your dxdiag report (click Start or WinKey-R, type in dxdiag and hit Enter, then in the window that opens, wait for it to finish and then click the Save All Information button).
