Yes, as the title says, the Blue Crown is the one that controls plagues. It is the secret to why Kallamar's forces were never sick, never injured and able to fight at heir full strength against Diana. It can inflict any sickness known upon its victims, or cause wounds to instantly worsen. However, just as much s the Blue Crown could cause such cruelty and hell, it could just as easily do the inverse. It can mend wounds faster than they can begin to cause lasting harm, boost the body's immune system to outright crush a virus, and even ensure full physical health.
The catch, as Diana has learned, is the Blue Crown does not see the world for what it is as mortals and the other Crowns do; at all times, it is seeing every single cell, microbe and particle with insane microscopic vision. When Kallamar looked at his siblings, he didn't see a frog, a cat, a worm or a spider; he saw moving, living clusters of cells moving around unless he focused.
Suffice to say, Diana isn't fond of having this manner of vision when the Blue Crown forces itself upon her; it can't reverse her blindness, as that is a condition that lost all hope of treatment at the edge of the axe blade, and she sure as hell can't stand the Crown thinks it's HELPING by enhancing her vision to so fine a degree! Fortunately, she found out if she focuses, or smacks the Blue Crown, it can let her control this microscopic vision, and let her focus on serving her flock as a doctor without peer.
But it isn't all bad. Yes, the microscopic vision the Crown gives makes her a nervous wreck when she's looking at something alive... But when she looks at something static, like the crystals she's holding here, it becomes relaxing. Instead of a million cells moving about, she cn see the fine patterns of how the crystal formed, see each and every arch, bridge and surface within that caused it to take shape. In this case, it's like she is looking within a geode. And believe me, the interior of a jewel is breathtaking when you look at it with a microscope.
So whenever she gets overwhelmed by the Crown, Diana takes out this string of rainbow jewels and looks at them, one by one, until she calms down again.
