Known in the world of Moonlight Angel is "Bloodlust," an Istrala's Demonic Focus is a mysterious state of mind and body in which their powers are amplified greatly and their bodies begin to react on instinct; much more quickly and ably than even an Istrala can normally manage.

If the Istrala in question happens to be an accomplished mage such as Phira, you'd best hope that you're not on the other side of their magical wrath.

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I guess this is KIND OF a spoiler? Kind of? But yes, "bloodlust" is merely a colloquial name for the violent state we've seen in the Istrala of Moonlight Angel. However, to the true Istrala, the condition is known as "Demonic Focus." And as what its purpose is? That, my friends, is a mystery for another day~.

Commission for the wonderful  jediscout1