There are loads of armor to obtain in The Legend of Zelda: Tears of the Kingdom. One of my favorites is the Mask of Awakening. Now, normally this armor piece is tied to the Link's Awakening amiibo, which is how I got it. But you can also get this mask in-game from the Thundra Plateau Cave. This just leaves figuring out where the Thundra Plateau Cave is and how to open it in Tears of the Kingdom.
Thundra Plateau Cave Location - TOTK
As the name suggests, you can find the Thundra Plateau Cave in the center of the Thundra Plateau. This location is found near Ludfo's Bog and Lindor's Brow. You can use Lindor's Brow Skyview Tower to reach this area quickly. Look for the square platform in the center of this location.
Related: How to Get Froggy Armor to Climb Wet Surfaces in Zelda Tears of the Kingdom (TOTK)
However, you may notice that there is no noticeable cave entrance. That is because you must solve a small puzzle before the entrance opens. This requires creativity and being at Thundra Plateau at the right time of day. Hopefully, your luck is better than mine because it constantly rained every time I tried to complete this.
How to open Thundra Plateau Cave in Zelda Tears of the Kingdom
To open Thundra Plateau Cave, you must align the shadow of the southern pillar with the shadow of the northern pillar. There are a couple of ways to do this, but if you have an axe or two, you can use the nearby mushrooms. Chop down a couple and form a tall tower of logs. Use Ultrahand to align these together and place it where the south shadow is.
The best time to try this is around noon. With the pillars lined up, angle it so that the shadow connects the southern pillar shadow with that of the north. If all goes well, you will open up the cave and can claim the Mask of Awakening inside.
For more information on The Legend of Zelda, check out All Amiibo Armor You Can Obtain Without Amiibo in Zelda Tears of the Kingdom and How to get Ember Armor in TOTK (Zelda Tears of the Kingdom) on Pro Game Guides.