Scripts

Could there be a mod that adds this feature? Because the Haven faction has different shields.
And where is this screenshot from?

Unlikely. But still, take a look at that developer script (campaign "Escape to Salvation", mission "The Veil Falls", when Lorenzo attacks Zehir). There is a startThread, but there are no errors.
It was present in the combat scripts even in the original.

Added after 39 seconds

No. It's just an NCF, it only adds creatures (although I don't know :D).

Yes, that's it.