Level 1 Demons Eyes

[Shazam]

I was following the Grimrock guide on gamepressure.net and it mentions that

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You can take the jewels from the demons eyes after you kill the skeleton warrior. The door closes though when you remove even one jewel.

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It says you will need one for a secret at the end of the game.

I'm playing on iPad so maybe it's slightly different?

[Komag]

Haven't played that version. If that's the case, then presumably they also changed the end secret. Or you could do one of those grab-and-move tricks to nab the gem right as you step through the gate, but then you can never go back!