I'm not entirely sure, but it's something that seems to be tied up with me and Viridi being spirits. Pretty sure Melinoe could do it too while she was here. It's like a generic blessing. Someone puts their faith in us, and we start picking up energy and we share...

It had me scared as hell at first because I did it to Rinoa and Tifa, and I didn't want my powers turned on again, especially not with Rinoa.