Sorry, it's not too glamorous and I just used the stock quantum tower image from the game but I like the idea very much:
Basically it just takes a pillar of a target cluster and adds one extra pillar to it. The idea is to help strengthen those duo/trio decks which might not want to go full rainbow with novas/supernovas/quantum pillars/quantum towers but still want to have a generic card to add more pillars to the cluster of choice. Supernovas are great for us rainbows with the diverse range of cards we have, but for duo/trio decks, it's hard to play a supernova in the first place with the 2 entropy (unless one of those elements is entropy, of course) and quantum towers are so slow at generating quantum of a specific type.
Playing it upgraded should have the same effect as playing a tower and add a quantum of the particular element type (or 3 random if played on a quantum pillar/tower cluster) at the time the card is played in addition to providing an additional quantum at the end of each turn.
As far as coding practicality, it seems quite doable since we already have earthquakes/quicksands/tsunami to reduce the number of pillars in a target cluster by three, so adding by one seems like it'd be hardly anything new that the code isn't already handling.
In terms of balance, I think it's quite a fair way to help strengthen those duo/trio decks which need a variety of quantums. It requires that at least one pillar/tower of the required type be played already so it's not a magic, choose your color kind of pillar adder, and it's an adder more than a pillar in itself. It would require some careful thought and planning to incorporate into decks to make sure they have at least one tower of the chosen color since it could not be played without already having a pillar of the required element up. It may also strengthen some rainbows if they are a bit heavier with one element than others and throw in a few mono-towers/pillars in addition to quantum towers/pillars. When they get the card, they can decide which type of quantum they're lacking and add to the appropriate cluster of choice.
For me, it would make something like a trio deck more appealing. Right now I stay away from those since it requires an awkward balance of three tower types or going quantum tower and then generally being deprived of those 3 elements you actually use. It's a flexible solution as well and while basic, can probably add some interesting dynamics to the game in the way that rainbow decks often introduce.
BTW, I wanted this card to have no element (like quantum pillars), but used entropy since I couldn't find a template for cards with no element.
