Master Key near Cache cages?

[London Pride]

Noticed someone mentioned in "the cache cave" thread there is a "master key" obtainable in the game that will open all the "cache" cages so the snake charmer/Thief/Paladin/Conjurer. How much further in the game is the master key? I'm agonising over which cache to go for

Thanks

[lazerbw]

SpoilerShow

When you beat the game through the true ending you get the island masters key that opens all locks and never disappears when unlocking, true ending requires you to get the 5th essence and defeat the secret boss though so you would need to figure it out or look it up

[sergregor]

I haven't found it myself but I would think something as powerful as the Master Key would be found very late in the game. By that time most of the items found in the caches won't be very useful.

I strongly recommend the

SpoilerShow

Snake Charmer cache. The serpent bracer is very helpful for an upcoming poison-heavy area, and the rope is amazing for another upcoming pit-heavy area, as well as throughout the rest of the game. The other caches have stuff that's either useless or only marginally better than stuff you can find elsewhere in the same areas.