Mother of All Warriors

You can find the answer in her bond story level 4.

Medb gives "birth" to warriors but not in a traditional way a woman would do. Her own blood can create homunculi-like beings that aren't that smart but the sheer number she can create is bound to even overwhelm a nation and bring it to its knees.

In fact, E Pluribus Unum (America) singularity revolves around Medb being given a Grail and as was in her past life, she has the desire to conquer and rule over a nation and create it in her own image.