Arc System Works heavily altered BlazBlue: Calamity Trigger’s core for BlazBlue: Continuum Shift. Guard Libra system? That’s gone and replaced with Guard Primers, blocks underneath your life bar that are whittled away with each hit. Each character has a different number of Guard Primers.
When these run out… actually, Aksys explains this way better than me in this video, which should get BlazBlue veterans up to speed on the changes.
Thanks for the tip about the video Mary!