Where do I get this 'Crystal Shard' ? Never heard about it... I did finish the game without cheating until reaching the 'Citadel Of Doom'. What was after, I can't remember.
If you don't know what the Crystal Shard is then you didn't "finish the game without cheating until the 'Citadel Of Doom'". That's a major part of the game. Getting to the Citadel of Doom is easy (no cheating required). Getting to it with everything completed is hard.
To get the Crystal Shard, you need to meet the wraith (or whatever the guy's name is) at the crypt at midnight and give him the bones from the huge underground maze. Finding the bones is a major pain in the ass. The wraith gives you the shard to get past the barrier in the Citadel of Doom.