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
In Kingdom Hearts 1, frost shards can be found primarily in the Ice Cream Shop area of the game, particularly in the world of Arendelle, though they can also be obtained by defeating certain enemies like the Ice Titan. Additionally, players can find frost shards in treasure chests located throughout different worlds. Lastly, they can also be synthesized at the Moogle shop once you've unlocked the synthesis feature.
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