Ah, I see. This is certainly an option as well.
I believe there have been a few discussions on this type of thing in design theory section already.
The types of effects that are available here are limited, but there are still many.
The biggest issue is that they need to be "targeting free" e.g. the effect should not require a player to target anything. Otherwise there will be complications.
Also, the effects should be low key / balanced enough that they could be used as a low / rainbow cost card.
There are a couple issues there:
1) Having a card cause a specified effect on discard is akin to giving that same effect to 0 cost card.
-One big difference here is that players will have to weigh using the free discard effect against the benefits of casting the card itself.
-This heavily limits how powerful the discard effect can be without making it overpowered
2) Since "discard cast spells" are effectively zero cost, it is important to be careful about stepping on the toes of other elements.
-E.g. any card that is "cast" by discarding can be splashed into any deck regardless of what element the card is or what quanta the deck has available.
Producing 1
on discard is low key, but is also versatile, and element specific.
Any other "discard to cast" spell effects need to be similarly balanced.
I'll have to mull over my options a bit.
I think this may be a good discussion to move to the design theory section.
