There are three locations where Link can obtain a Kite Shield. The first is in a metal Treasure Chest in the ground in an enemy giant skull at North Tabantha Snowfield that Link must use Magnesis to pull out of the ground. The second Kite Shield can be found in a Treasure Chest in an ice formation at Hebra Headspring.

How rare is the kite shield?

It's one of the rarest shields in the game. Only four Kite Shields exist within Hyrule (three in the base game, one in Master Mode), and once broken do not reappear, rendering them irrecoverable. Neither Rito nor monsters are shown wielding them.

How do you get the kite shield in Valhalla?

The Kite Shield is a Heavy Shield that falls under the bear-aligned skill tree. The Kite Shield can be found by exploring Wandrie, in the Grantebridgescire area.