Oh ho! I like this concept. We may need to return to this well a few times in the future...

Design a counterspell. You can't use a mana cost that's already been used in this challenge: eg. the first entry is likely to be , or , but after a few entries, you will probably find yourself trying to create a U or 4UU counterspell. Those are harder to make relevant, but I think (hope) it's quite possible to do so without too much repition.

Notes:
- Your first card should be for a mana cost not yet used.
- After that, it's ok to propose some alternatives with already used mana costs if you want to, but try to at least submit a card at a new cost at the same time.
- Multicolour, colourless, Hybrid mana, X-spells, phyrexian mana, etc, all count as different, so , , , , etc are all valid costs.
- Additional/alternative costs are fine, but don't count towards the "different mana cost" restriction. But don't use an alternate cost which is mana, if the real mana cost will never be used :)
- You should probably stick to wizard's guidelines which are that almost all counters have in, and any non-conditional counters have in. But there are exceptions (white Memory Lapse was proposed for Planar Chaos, several spells counter a blue instant) feel free to make more if you think they're appropriate.
- It's fine for the spell to be very situational, or to do other things as well as countering, as long as it. I'm not sure where the line is drawn: I think "exile target spell" counts, but "target creature gains hexproof" doesn't, even though technically the second counters a spell and the first doesn't.
- Don't grab several of the "obvious" costs on the trot without giving other people a chance to submit something for them, but feel free to submit any number of cards with multicolour or very expensive costs, etc, or to submit another card with an "obvious" cost after a little while.

jmg: Thank you! Yeah, it seemed a good idea when I thoguht of it. I hope it doesn't get too repetitive :)

­Protective Ward. First submission is white! (Costs .)

­Beastify costing .
Also, Ethercoil costing .
Also, Merfolk Titan costing

(((Mana Lightning))) costing

­Go away, I'm busy costing and it's a proper Counterspell 'counter target spell' too, dammit.

­Mana Birds costing isn't quite Beastify

­Control Magic costing of course. How it should have been.

Added Temporal Crash, costing and
­Gate to Eternity, costing .

Added (((Manamorph))) costing

I have an entry at , but submission is currently failing. Bagsy that cost!

Also Caught in the Wash at

Let's have another new one. ­Canopic Jar at

Created Omnibus Charm at .

Added Vitriolic Refusal, because I was really afraid that someone would steal away from me. :D

Added (((Syphon Python))) for
Mystic Snake's little/big brother

Added Overcharge for

I wanted , but Vitenka got there first. Eventually I found a cost that's not yet been taken: Reject the Obscure at .

LOL. Yeah, so far in non-phyrexian blue we've had , , , , , , , , .

If I'm right, , , , are available, plus all 6CMC, plus all-U mana costs at everything above 2 :)

­You cannot defeat me is
­(See Cost) is
­Cancel (Not the time spiral one) is

Finally managed to submit Adaptive Denial at

Oh. I made Grave Denial and forgot to list it here.

I made Deny the Unnatural, which costs and is probably too much of a color pie stretch to be printed.

Added (((Denying Winds))) for
Inspired by L2i0n0k7's Deny the Unnatural to explore green counterspells

I made Oppress.

Link filled up the and slots. I tried to fill up the 6cc slot, but failed, instead taking up with Metabolize Thoughts.

Also, added "Voidmage Acolyte" and costed it at for your amusement.

Edit: Oh, huh, weird. I tried giving this the name of ".", then "l" when I found out I couldn't auto-card that... but neither of those auto-carded. The flipped side auto-cards, though. Good to know.

And at , Lesser Remand

Added (((Mind Shrapnel))) for
Considered making it and combining Cancel with Hymn to Tourach but that was a bit too nasty so halved the hymn effect.
This could easily be recosted at or even

And a silver bordered card, Fowl Ball at :)

Current slots used so that my brain doesn't explode:
­
­,
­, ,
­, , ,
­
­, , ,
­,
­
­
­, ,
­, ,
­
­, , , , , , , , , , , , , ,

Strangely, nobody has done Cancel mana yet... probably because that's the baseline, and the double-blue makes it so that it can't be situational... so making it equal to and a hard counter is kind of tough. Edit: Alex got that now.

Added Mental Headbutt at and edited my previous post.

added (((Mana Freeze))) for as nobody had used snow mana so far.

@jmg, Oh, thanks for making the chart, that's really helpful.
@Camruth, oh yes, nice snow mana.

And also, Casting Edict.

I took jmg's comment on Cancel mana as a challenge, and created Arrogance of the Quick.

Added (((Withered Link))) for

after feedback this has become which is fine

­Mental Headbutt became after people made some accurate responses to it. Spicier there anyway. Editing my previous list...

Oh, and because we haven't got absurd enough, I added Undeniable Proof.

­Research Grant Depleted

­Time Split at For when you absotively posalutely need an opponent to have not cast that.

And Extreme Reversal at for another massive counterspell.

I just recently made Spell Harvest for a different challenge, which works here, but I also made Flurry! Slightly more snow mana than the other one.