The Oathbound
Mercedes Lackey
Tarma and Kethry are unlikely companions, mage and warrior. Bound together to go against bandits, they’ve stuck together to get Tarma home to the plains to claim her birthright. There’s plenty in the way before the can fulfill that though.

Most of the story seems to be told from the perspective of Tarma, which suits me just fine, just haven’t read a bunch about Kerowyn (Kethry’s granddaughter). Tarma is a sexless warrior, absolutely skilled in the blade. She’s not cold though, she cares about her people and Kethry.
This is the first outing of the sword, Need. Need plays an important role in ‘By the Sword’ and also the novels with Elspeth and Darkwind (the Winds trilogy).