In every dungeon, there is a large, pointed, sinister looking chest. Inside is the Boss Key. Usually you have to solve a puzzle or defeat a monster to get to it. If you find the Dungeon Map, that will help you quite a lot.
There is one in each dungeon.
In the first dungeon.. If you have a compass, you can find them easily
Try and find your way through the dungeon to a door with a gold chains on it.go near it, interact with the door,and fight the boss!
Find the big key.
You find it after defeating the mini-boss in the Goron Mines (2nd dungeon)
You get it in the sky temple when you beat the mini boss.
Where montain dungeon twilight full drio
Midnas theory that the spirits have them is wrong, however the spirits hid them in the first 3 dungeons of the game; the forest temple, goron mines, and the lakebed temple. You will recieve the fused shadow after the dungeon boss is defeated.
8 in all, including the four you have to find before the mini-boss
There is no way to get the Gale Boomerang without beating the minor boss in the forest temple (the monkey chief).
You have to find it in the temple of time, which is hidden in the sacred forest. if memory serves, you will find it after you defeat the mini boss.
you have to find the three key shards which open to the boss gate its very easy