Tentative plan for Eirny to contribute to the battle, unless someone has better ideas for her;
Eirny is going to stoke an aspect on her Weapon Flow-Reading Trick. This basically gives her a false Frenzy where she can read where weapons are going and how to perfectly avoid/counter them, and by using an aspect it lasts a Long Time. She's then going to either;
A. Act as support for our front line, dancing through to where she sees/expects dangers, to destroy them
or
B. Invite the horde of skeletons to face her and her blade, as she ultra instincts through the fights and cuts many a skeleton.
A is preferred, but would be more work for IF running one on ones, unless they just want the freedom to use Eirny as a get out of jail free card for X people.
She doesn't otherwise have much that she can do. She's fast, she's got good reactions, she's great with her blade, and... that's all of it.
I have not made the most utility-capable person.