NY Laegjarn

I'm probably gonna go for a defencive duelist.
Her high speed and def are great.

Maybe something simple as fury and a slaying lance.

I personally am going to run her with her weapon which has chill def and runs chill spd in her b slot with fury and an atk refined Wasaga+ with hone cavalry and for a sacred seal distant def, close def, an atk/def bond, or atk smoke.

For me, it's likely to be:

Base Kit
Speed Refine
Possible New Assist
Fury
Res Tactic Seal

She's naturally built to be a support unit with Double Chill and easy access to Double Tactics.