Mercedes Lackey

There are tons written by Mercedes Lackey.

She's best known for her Valdemar series.

These are just a few of her prolific works.

Vows & Honor
The Oathbound

Kerowyn's Tale
By the Sword

Elemental Masters

Fire Rose, The
Gates of Sleep
Serpent's Shadow, The
Phoenyx And Ashes
Wizard of London

Bardic universe:

Bardic Voices
Lark and the Wren
Robin & the Kestrel, The
Eagle and the Nightingales
Four and Twenty Blackbirds
Bardic Choices
Cast of Corbies, A (1994) by Mercedes Lackey, Josepha Sherman