I was under the impression it's the type of spell you reserve for boss animations...? you know, the kind of attacks where you can't even target them and stack to mitigate the unavoidable damage.
I'm gonna get lynched to oblivion for this, but because I love bubbles and barriers type of skills, I actually like the concept of CU. That said, I agree it should be stronger, even more so than either Asylum or Sacred Soil if it's to be used less...freely.
