The air pirates in port royal they are the only ones that drop them
the beast castle the fat guys or the lance
I believe it's either the Gargoyle Nights or the Sky Pirates that both drop either dark gems or dark crystals respectively. They can be found in Beast's Castle and The Land of Dragons
'Dark Crystals' are dropped by Air Pirates (located in Port Royal and The Land Of Dragons)
Your Kingdom Hearts might be different to mine, but I think the one you're talking about is Oblivion.
Kingdom Hearts is an entity formed from the gathering of hearts. Hearts gather into Kingdom Hearts when Heartles and Nobodies are vanquished with the power of the keyblade (otherwise the hearts would just reform into Heartless again). Kingdom Hearts was originally thought to be a dark or evil entity, but as Sora learned from his adventures in the first game; "Kingdom Hearts is light".
The World That Never Was
I had a dream where I went to the kingdom hearts worlds and had my own adventure it was pretty interesting.......and a little dark at times X3
There is no such thing as a dark crystal, although you might be talking about lucid.
By beat the life out of him
No, the darkness is just that; Darkness
Once you defeat sephiroth at the dark depths
well, for sure, shadows have dark shards