Can we clarify that every spell has an effect?

I think there are also some timing considerations here.

If you have 2 stars and you cast Doom Cloud but also get burned presumably the spell would still succeed and you’d be left at 0 spells (assuming https://blognomic.com/archive/negative_energy1 passes). Which I think is the right behavior, but do we need to clarify it?

I don’t think it’s technically necessary to require that each spell has an effect, but it would be pretty pointless to define a spell without one. I’ll rephrase it though so you can’t do that.

If you select Doom Cloud and start the duel with 2 stars, then get burned and don’t make up at least 1 star before your turn somehow, you’ll have 0 stars when you cast Doom Cloud so it’ll fail. I think that adds a level of strategy since you’ll know the turn order before the duel.

Ok oops, for some reason I thought spells were resolved in order of the ring, but I just re-read the rules and realized it says they are cast simultaneously

You’re right then, ostensibly as long as you have enough stars at the start of the duel then it will still succeed, although all spells being casted simultaneously does kind of create a paradox when casting a spell depends on some gamestate that is changed by the effect of another spell.

Unless / until we have a way of determining spell casting order, we should assume that it needs to be possible to resolve spells simultaneously.