That is a bug. A couple of other people ran into that, as well, but were able to finish the fight normally by reloading a save before it started and redoing it.

If you wouldn't mind, please email supportdos@larian.com, with your save at this point, maybe one mid fight, if available, and a save just before the fight, like the autosave on the stairs (or a Dropbox or Google drive link, etc).


For Windows you can use the report.zip file generated by the D:OS EE Analysis Tool.
Extract the zip file somewhere and run AnalysisTool.exe. When that loads, browse to the install folder (if it is not automatically detected), optionally run the tests first, and then generate a report (it will be saved in the same location as the Analysis Tool).

The report will contain system and game information, as well as your saved games. To reduce the file size, you can delete most of the saves from the zip (double click the zip file to open it in Windows Explorer, then browse down to the savegames and savegames_patch folders).


For OSX, saves can be zipped by right clicking the folder(s) and selecting Compress, in the folder:
~/Documents/Larian Studios/Divinity Original Sin Enhanced Edition/PlayerProfiles/<ProfileName>/Savegames_patch

Linux is similar, with the saves in the home directory.