Platinum Staff | Electrum Staff

[Shantu]

Strong effects will never work when costing Other quanta. The most common way to try balancing it is to increase the cost of the card, but that fixes nothing, since rainbows are hardly hindered by the ultra-high cost (remember, triple quanta generation) while it becomes unplayable for non-rainbows.

Would work a lot  better if it costed a lot less (like 3) and increased spell damage by only 1 and maybe dealt a little damage (1). More fitting for an other card.

[furballdn]

Rather than increasing weapons cost, what if it increased Spell cost?  After all, even if it acts as an amplifier, you'd need to introduce more energy [e.g. quanta] to make the effects of the spell larger.

Already mentioned. It makes your cards have more space advantage. It's the same reason people use deadly poison over poison despite poison having a better damage/cost ratio.

Why not make this one of those other quanta, was it mirror quanta or something?

[OdinVanguard]

Perhaps it would help if the ability required activation. E.g.
"Weapon.
3: The next 2 spells you cast cause double Damage and Effects."

That would be a little easier to balance I think