Cluster-Maker.

[Sarick]

True, but the likelihood of being able to cluster crystals in the field would be low, more likely to be a NPC which to me would be worse.

I was thinking more along the lines of this..

Stage one syth >>

Item: Inferno Crystal
Element: Fire Crystal
Ingredients: Fire Crystal x5

Stage 2 >>
Item: Fire Cluster
Element: Fire Crystal
Ingredients:Inferno Crystal X1, Fire Crystal X5

The reason 2 stages would be do to the 8 ingredient limit.

Another option would be to give the players a quested KEY ITEM or bought item that allowed them to fuse crystals into clusters with a command.

Elemental Forge, maybe?