+3 gems for every neighboring card with gem cost
Does this only refer to the two (or one if in position 1 or 8) cards neighboring Ethereal chain, or will it look at the neighboring cards of those as well if they are valid? As it is now, it sounds like it should only look at the two neighbors, but named as a chain, the latter seems a possible interpretation.
It would need rebalancing, but it could be more interesting that way. Or perhaps introduce an Uncommon version as well that does that.