My DM is encouraging us to come up with a homebrew spell.  We're level 6 and I'm playing a Circle of Stars Druid.  I just wanted to get some feedback on the spell:

It's basically fireball, except CON save instead of DEX, 4d8 Radiant damage instead of 8d6 Fire, and on a failed save it also blinds until the end of an afflicted creatures next turn.  Otherwise it's the same spell level, range, and radius.  My initial thought is this is fairly balanced.  My only concern is that blinded is a pretty strong condition and I'm wondering if I'm overshooting here. 

Tradeoffs: 

PRO:  Better damage type, Blind

CON: Less damage, CON saves are generally harder than DEX

I think this is probably fair, though blinded is a bit on the strong side for a third level spell. I might consider making it a fourth level and adding 1d8 to the dice damage. 

It seems fine to me. Making it a CON save is a downgrade, and it takes a damage hit too. As long as you're playing blind correctly - you still know where everyone is unless they use the hide action, you just have disadvantage to hit them - then I think the effect is fine.

Fireball is already considered Top of the Line for a 3rd level spell.  Adding Blind is too strong in my opinion. Plus Radiant is a better damage type. 

What you have here is a 4th or 5th level spell.

I would have you reduce the damage, reduce the area effect, or raise the level.

Between the fact Con saves are generally a more commonly proficient save type for monsters than Dex, and that you’re looking at approximately a 33% reduction in damage, I think the improved damage type and the added condition are okay.

Thanks for the feedback everyone.  I tend to agree that it is very strong but only on the same tier as fireball.  I'll let you know how it plays!