Mods Used:
- Radiance (Default Config)
- Hero Mod

Occurs with what seems like any video quality (low, med, high) when 'Waves Quality' is 'off'. This happens consistently when the boss uses "Everlasting Rainbow" for the first time and it renders the other boss attacks invisible (except for the boss dash) along with the player and the GUI (even when inventory is open).
I tried checking the log files to see if there were any error present and there were none at all.

Other things I tested (keeping 'Waves Quality' off):
- Video options such as 'Blood and Gore', 'Heat Distortion', 'Storm Effects', and 'Windy Environment' seem to not contribute to this error and same with parallax.
- Disabling/Enabling 'Reduced Flashing' in the mod config doesn't fix the error and in general the other visual tweaks did not fix this issue.