The Heralds of Valdemar
by Mercedes Lackey
I humbly suggest that you read the books in this order:
Vows and Honor
The Oathbound
Oathbreakers
Oathblood
The Heralds of Valdemar
Arrows of the Queen
Arrow's Flight
Arrow's Fall
The Last Herald-Mage
Magic's Pawn
Magic's Promise
Magic's Price
Kerowyn's Tale
By The Sword
The Mage Winds
Winds of Fate
Winds of Change
Winds of Fury
The Mage Wars
The Black Gryphon
The White Gryphon
The Silver Gryphon
The Mage Storms
Storm Warning
Storm Rising
Storm Breaking
Owlflight
Owlsight
Owlknight
Sword of Ice
and other Tales of Valdemar