To make a shard you combine 4 ingredient and a power-cell, doing so gives you a type of essence. It takes 3 specific essences to make a specific shard. You only TECHNICALLY need 1 large shard- However to make a "supreme" GS item, it takesa "double imbued" shard. This uses SIX total essences, not 3. To make it you make the FIRST large shard, then make the 3 other essences, and combine them WITH the original large-shard, to make a double imbued large shard.
I used the first 3 large essences to make 1 large shard, and the second 3 essences to make a SEPERATE large shard, instead of combining them ONTO the first original shard. Again I was under the impression you just "added the second large shard" to the GS item (as you had done with the small and medium) to upgrade it to a supreme, and had no clue i was supposed to "double imbue" the original supreme shard.
Such a stupid let down on my own part. Its taken me months to acquire the materials to do just this one
Im not a very rich character and only have a single capped char.