defeat the small jellyfish in atlantica
you have to battle those blue things that fly around
You can use shards along with other various things to synthesize new items
Mythril Shards either come out of chests, or usually the Shadow heartless.
well, for sure, shadows have dark shards
In Kingdom Hearts II Final Mix, Frost Crystal (shard) can be found in a chest at the Cavern of Remembrance: Depths.
Dense Shards are found in Twilight Town, Hollow Bastion, The World That Never Was, and Beasts Castle
I don't think you can find Mythril Shards in Heartless. Only in Treasure Chests around other worlds.
frost wire or lime wire
Living Bone
Go to The Hall Of Cornerstone and fight the enemies there.
for number one it is found at the blue floating heartless
Frost stones can usually be found in Abrabah, with the Fortune-teller or the little ice cube heartless.