To be honest, Deluge might be a lot less exciting if you had to pay the mana cost for everything, but a lot easier to balance (and still, a crazy good ability. Consuming Vapors, for example, saw heavy use in a number of tier one tournament decks... often with no other arcane spell in the player's deck.)

I was thinking that Deluge could be this set's Cascade/Rebound/Phyrexian mana "freebie" keyword. I'm realizing now that it's a lot more powerful than I thought at first. I'm going to change it to something easier to balance, which means, like your suggestion, adding a mana cost to Deluge.

Okay, I was thinking of changing Deluge to "You may cast this spell for its deluge cost from your hand or graveyard whenever you cast another spell with deluge that costs more." However, while that adds a cost, it also means you can cast any number of, for example, two-cost Deluge cards when you cast a deluge card with 3 CMC. It also opens up confusion as to whether "costs more" refers to the converted mana cost or the deluge cost. At least with the current version, you can only cast one spell of each CMC.

Deluge is currently "When you cast this spell, you may cast a spell with with deluge that costs less from your hand or graveyard without paying its mana cost."

Possible alternate versions:

• When you cast this spell, you may cast a spell with with deluge that costs less from your graveyard without paying its mana cost. Then exile that spell.
• When you cast this spell, you may cast a spell that costs less from your hand without paying its mana cost.

The first alternate is sort of like cascade-flashback. The second is like a slightly worse cascade (which was quite powerful, so I'm okay with that.)

Are you actively trying to avoid abusive combos with constantly casting the same non-deluge sorcery over and over again from your graveyard? Because I was going to suggest it, but yeah... it's probably abusive to keep casting Time Warp off of a string of one-cost deluge spells...

It's a shame, though, since that would have made Deluge non-parasitic. Though, I suppose you could get away with it if you exiled the spell. It would offer more variance, too, than deluging into the same spell over and over again, and reinforce "Blue likes instants/sorceries" since you need a lot more to make deluge work for you, if that's what you're going for.

I'm a little unclear as to what you're suggesting. Are you suggesting deluge should be be "When you cat this spell, you may cast an instant or sorcery spell from your graveyard that costs less without paying its mana cost. If you do, exile that work when it resolves?"

Also I'm unsure how any version of deluge would allow you to cast Time Warp using one-cost spells.

As the ability reads now. You can cast a 5-CMC spell with Deluge then a 4-cmc deluge spell from hand or graveyard for free, then a 3-cmc from hand or graveyard for free etc. I think Deluge needs to check that you spent mana on the spell before it lets you get another one for free.

I think that's the point: if you can get the 3-cost Deluge spell, the 2-cost Deluge spell and the 1-cost Deluge spell into your graveyard, you get them all every time you cast a bigger Deluge spell. But that's actually quite a big "if". I think it'd play interestingly but not brokenly.

If it just read from graveyard sure but it currently reads from hand and graveyard. Also this means a heavy Deluge deck will just recast most any spell it's cast that game so long as it's cheaper than the one it pays mana for. I just think that as is this mechanic is just way too strong. If it exiled the recast spell some how it would be far more balanced.

Yes. It doesn't care about casting order or anything - just "Ok, I casts my CMC X+1 spell, and splice onto it every CMC X or less spell I have drawn or cast so far this game"

Which is... stupidly powerful. Even if every individual effect is relatively small.

Maybe make a deluge trigger exile the card? So you get one free use from hand (but that's costing you a card) or you get a second casting from graveyard (but only one) which is still nice but not as broken and needs a little more thought than just using them every time.

Also - even if this IS good, it's gonna wither like arcane did out of set; there's nothing out-of-set to trigger it. So quite parasitic.

I don't know how this mechanic is going to be balanced, but FWIW, I love the feel of it.

I'm pretty keen on changing deluge from its current functionality. I've made two possible suggestions above for changes, and I'll add a third to the list:

• "When you cast this spell, you may cast an instant or sorcery card that costs less from your graveyard without paying it's mana cost."

This removes concerns of parasitism, though you'd still be able to chain deluge spells together. Honestly, the strength of that depends on there strength of the deluge spells. I would just have to be careful.
All this conversation is moot unless I actually decide to use deluge, which I may not.

I like the latest version. I was thinking something similar, working with non-deluge cards is very nice.

Ideally I'd like it that you can build up to a big deluge by playing a 1-cost spell, a 2-cost deluge spell getting both, and a 3-cost deluge spell getting all three, because that's awesome, but not that you can play a 1-cost removal spell, and then just keep hammering it with repeated 2- and 3-cost deluge spells because that's boring, and all the cards would have to be a lot more expensive. But I'm not sure how to achieve that.

I should probably add the tag "If you do, exile that spell."