To obtain the Mirror Shield you simply have to combine your normal shield with a Zonai Mirror in Zelda: Tears of the Kingdom.
Mirror Shield also known as Zonai Mirror Shield, makes a return from the prequel to Zelda: Tears of the Kingdom. It can not only deflect enemy attacks but in the presence of sunlight, moonlight, or any other light source, Mirror Shield can reflect it back into your enemy’s eyes to dazzle them.
The dazzle will stagger your foes, making them drop their weapons while giving you ample window to launch an attack against them. It can also be pretty effective in Lightening Temple for solving Light Puzzles and the Queen Gibdo boss fight.
It appears as a large stadium light attached to your shield when in full effect which is pretty fun to use as you watch your enemies scramble about.
