Most of those spells are excellent, but counterstrike is almost strictly better than render silent, which itself is already very powerful, so I would recommend that you somehow reduce its power to balance it. I also believe that spellsnatch should have a limit on the duration for which it can be cast from exile (perhaps until then end of the turn?).
It uses more colors than Render Silent, so it's allowed to be a little stronger. I'd sooner add to its mana cost than reduce its strength, but I suppose you could reduce the damage to 2.
I'm not okay with 'exile target spell' effects at 3 cmc. It's just a way to get around 'can't be countered' effects. I would be fine to do something more like Dissipate at 3 cmc with extra stuff from the difficulty of 3 color, but not with breaking the 'can't be countered' condition at 3 cmc, which is normally the 'hard counter' standard set up in Modern by stuff like Cancel.
Mindbreak Trap at normally 4 cmc is where that kind of effect should start turning up, even considering multicolor.
I used straight exile instead of Dissipate-style exile to save space, not to get around "can't be countered" effects. If costing it at 1GBU feels better, by all means. Or you could write it out as Dissipate meets Psychic Intrusion, but then you likely can't include flavor text.
I find the trick to designing affinity cards is to make it so you can play the affinity spell when you'd be able to play the spell as it would be costed without affinity as long as you're on curve. Immerse in Thought is a fine example: When you have three Islands, you only need to pay 2U to play it, the same you would with Divination. If you continue to play more Islands, however, Immerse's cost goes down further. The affinity Golems are the same way. I call this phenomenon the affinity threshold, the point where the card can first be played when you support the affinity. Affinity for basic land types is the easiest category by which to apply this tool, but other categories can also take into account the possibility that you're playing one permanent of the relevant category each turn.
The color weight suggestion is an interesting one as it doesn't disrupt the threshold while imposing a slightly higher minimum cost and makes sense as you're encouraged to devote to the color anyway.
Give me a niche to fill, and I'll usually design a card to fill it.
CountershieldGWU
Instant
Counter target noncreature spell. You and permanents you control gain hexproof until end of turn.
Dire BacklashUBR
Instant
Counter target creature spell. ~ deals damage equal to that spell's power to its controller. That player can't gain life this turn. "I love irony." - Eliza of the Keep
CounterstrikeURW
Instant
Counter target spell. ~ deals 3 damage to that spell's controller. That player can't cast spells this turn. The mage's head ached. Was the blow physical, mental, or both...?
SpellsnatchGBU
Instant
Exile target spell. You may cast that card for as long as it remains exiled and you may spend mana as though it were mana of any color to cast that spell. "What a splendid idea. I'm glad you thought of it."
Actually, redirecting damage makes less sense with a toughness boost than target redirection. Why bother raising the toughness when you can just redirect the damage anyway? With the target redirection, the toughness boost serves to help the creature survive the damage it can't redirect, namely combat damage and nontargeted damage such as Scouring Sands.
Based on what we've seen of the dragon bones, I'm guessing most dragons will follow a similar body type but with differing characteristics like crests and of course coloration. Since soft wedge will be present in FRF thanks to hybrid mana, perhaps we'll see a cycle of CD/E Dragons?
Eh, rituals in a set with affinity will feel just a tad bit pointless. I guess there will be cards without affinity that you could ritual into but if the ritual itself requires a decent number of lands to even play, what's the point? I would recommend something closer to this:
Mountaintop Ritual5R
Instant {U}
Affinity for Mountains
Add RRRRR to your mana pool.
Consider that one Mountain not only covers the but also takes off the cost. By turn three, if you have three mountains you can cast this spell for 2R, accelerating by two mana. At five mountains you can ramp to nine mana.
I like your thinking, but I would suggest a different wording.
Mirror Shield 4
Artifact - Equipment {R}
Flash
When ~ enters the battlefield, you may attach it to target creature.
Equipped creature gets +0/+2 and has "2: Change the target of target spell or ability if it targets only this creature."
Equip 2
The best way to implement a redirection ability is as a surprise so the opponent doesn't see it coming. I would suggest something like this:
Mirror Shield 4
Artifact - Equipment {R}
Flash
When ~ enters the battlefield, you may attach it to target creature.
Equipped creature gets +0/+2 and has "Whenever this creature becomes the target of a spell or ability with a single target, you may change the target of that spell or ability."
Equip 2
I mean, it could be a thing again. But the brokenness of affinity in Mirrodin block was exactly because of the "free spell" effect that you're trying to achieve. WotC has said that, were they ever to do affinity again (and it looks increasingly like they never will) it would be for something that's harder to amass in quantity than artifacts. Basic lands are probably the least likely candidate for affinity's return.
Actually, basic lands are a rather fitting choice. The net result isn't far removed from monocolor hybrid; you get the card for approximately half price if you're devoted to the right color. That was the genius behind the Darksteel golems: you only needed to get halfway before they could be played, and any of them could be played turn 3-4.
Now, in a less artifact-heavy set, you're likely to see monocolor cards with affinity for the appropriate land type, though multicolor uncommons or rares with affinity for two different land types would be interesting to see. Let's explore some examples:
Leonin Fieldhunter3W
Creature - Cat Warrior
Affinity for Plains
2/2
Counterwave4UU
Instant
Affinity for Islands
Counter target spell.
Deadly Swamp Gas4B
Instant
Affinity for Swamps
Target creature gets -3/-3 until end of turn.
Rock Toss3R
Instant
Affinity for Mountains
~ deals 3 damage to target creature or player.
Woodland Baloth6GG
Creature - Beast
Affinity for Forests
4/4
As an alternative, such cards could simply always cost 3 and feature the rules text, "Cast this card face-down as a 2/2 creature. You may turn it face up at any time for (mana cost)." Perhaps it could even be an evolved keyword similar to typecycling or multikicker. That way the missing cmc problem is averted.
Ainok Trapper3
(W) Creature - Hound Warrior
Conceal 1W(Cast this card face-down as a 2/2 creature. You may turn it face up at any time for its conceal cost.)
When ~ is turned face up, you may tap target creature. If you do, prevent all damage that creature would deal this turn.
2/2
Consider that in a given multicolor faction set each color will see use in two factions on average. In Shards and KTK block, each color sees use in three factions. In RAV and RTR, each color sees use in a total of four factions. In a prospective ten trios block, each color is divided between six factions. Granted you could separate the trios the way RTR separates the guilds, with five in one large set and another five in the other. They have a hard enough time getting ten pairs to work in a single set; ten trios most likely ain't happening.
As for the mana base, aside from uncommon trilands you can print common duals, allies in the shard set and enemies in the wedge set, plus perhaps one rare rainbowland for each set. Mana rocks can mirror the lands. In a given set, that amounts to 22 mana sources, 44 total between the two sets. While a L/L block could in theory accomodate ten trios, I'd think you'd want a LsL block for drafting and helping to "glue" the large sets together.
Personally though I like the idea that dualcolor sets like Ravnica get to have more factions to counterbalance the fact that each of its factions is "simpler" than those in a tricolor block. It's a nice balancing act.
I throw my vote in for enemy manlands and fastlands. But you know a cycle I'd like to see that hasn't even been done yet? Cycling duals, like so:
WU Cycleland
Land
~ enters the battlefield tapped.
: Add or to your mana pool.
Cycling 1(W/U)
A cycle like this would have served Shards well, I'd think. One problem with lands like these compared to the monocolor cyclelands from Urza's Saga and Onslaught is that you generally want to play your duals early in the game, ETB tapped or not, while lands with cycling generally encourage you to toss them for another card unless you absolutely need the mana. I suppose a second way they could do them would be similar to Cluestones:
WU Clueland
Land
~ enters the battlefield tapped.
: Add or to your mana pool. WU, , Sacrifice ~: Draw a card.
The benefit of this cycle is that it encourages you to actually play the land before tossing it for the card, and the ETBT helps balance it compared to the Cluestones. It helps that such a cycle would be easier to reprint since it doesn't use a distinct keyword.
It uses more colors than Render Silent, so it's allowed to be a little stronger. I'd sooner add to its mana cost than reduce its strength, but I suppose you could reduce the damage to 2.
What about Psychic Intrusion? That doesn't impose a time limit.
I used straight exile instead of Dissipate-style exile to save space, not to get around "can't be countered" effects. If costing it at 1GBU feels better, by all means. Or you could write it out as Dissipate meets Psychic Intrusion, but then you likely can't include flavor text.
The color weight suggestion is an interesting one as it doesn't disrupt the threshold while imposing a slightly higher minimum cost and makes sense as you're encouraged to devote to the color anyway.
Countershield GWU
Instant
Counter target noncreature spell. You and permanents you control gain hexproof until end of turn.
Dire Backlash UBR
Instant
Counter target creature spell. ~ deals damage equal to that spell's power to its controller. That player can't gain life this turn.
"I love irony." - Eliza of the Keep
Counterstrike URW
Instant
Counter target spell. ~ deals 3 damage to that spell's controller. That player can't cast spells this turn.
The mage's head ached. Was the blow physical, mental, or both...?
Spellsnatch GBU
Instant
Exile target spell. You may cast that card for as long as it remains exiled and you may spend mana as though it were mana of any color to cast that spell.
"What a splendid idea. I'm glad you thought of it."
Mountaintop Ritual 5R
Instant {U}
Affinity for Mountains
Add RRRRR to your mana pool.
Consider that one Mountain not only covers the but also takes off the cost. By turn three, if you have three mountains you can cast this spell for 2R, accelerating by two mana. At five mountains you can ramp to nine mana.
Mirror Shield 4
Artifact - Equipment {R}
Flash
When ~ enters the battlefield, you may attach it to target creature.
Equipped creature gets +0/+2 and has "2: Change the target of target spell or ability if it targets only this creature."
Equip 2
Mirror Shield 4
Artifact - Equipment {R}
Flash
When ~ enters the battlefield, you may attach it to target creature.
Equipped creature gets +0/+2 and has "Whenever this creature becomes the target of a spell or ability with a single target, you may change the target of that spell or ability."
Equip 2
Actually, basic lands are a rather fitting choice. The net result isn't far removed from monocolor hybrid; you get the card for approximately half price if you're devoted to the right color. That was the genius behind the Darksteel golems: you only needed to get halfway before they could be played, and any of them could be played turn 3-4.
Now, in a less artifact-heavy set, you're likely to see monocolor cards with affinity for the appropriate land type, though multicolor uncommons or rares with affinity for two different land types would be interesting to see. Let's explore some examples:
Leonin Fieldhunter 3W
Creature - Cat Warrior
Affinity for Plains
2/2
Counterwave 4UU
Instant
Affinity for Islands
Counter target spell.
Deadly Swamp Gas 4B
Instant
Affinity for Swamps
Target creature gets -3/-3 until end of turn.
Rock Toss 3R
Instant
Affinity for Mountains
~ deals 3 damage to target creature or player.
Woodland Baloth 6GG
Creature - Beast
Affinity for Forests
4/4
Ainok Trapper 3
(W) Creature - Hound Warrior
Conceal 1W (Cast this card face-down as a 2/2 creature. You may turn it face up at any time for its conceal cost.)
When ~ is turned face up, you may tap target creature. If you do, prevent all damage that creature would deal this turn.
2/2
As for the mana base, aside from uncommon trilands you can print common duals, allies in the shard set and enemies in the wedge set, plus perhaps one rare rainbowland for each set. Mana rocks can mirror the lands. In a given set, that amounts to 22 mana sources, 44 total between the two sets. While a L/L block could in theory accomodate ten trios, I'd think you'd want a LsL block for drafting and helping to "glue" the large sets together.
Personally though I like the idea that dualcolor sets like Ravnica get to have more factions to counterbalance the fact that each of its factions is "simpler" than those in a tricolor block. It's a nice balancing act.
WU Cycleland
Land
~ enters the battlefield tapped.
: Add or to your mana pool.
Cycling 1(W/U)
A cycle like this would have served Shards well, I'd think. One problem with lands like these compared to the monocolor cyclelands from Urza's Saga and Onslaught is that you generally want to play your duals early in the game, ETB tapped or not, while lands with cycling generally encourage you to toss them for another card unless you absolutely need the mana. I suppose a second way they could do them would be similar to Cluestones:
WU Clueland
Land
~ enters the battlefield tapped.
: Add or to your mana pool.
WU, , Sacrifice ~: Draw a card.
The benefit of this cycle is that it encourages you to actually play the land before tossing it for the card, and the ETBT helps balance it compared to the Cluestones. It helps that such a cycle would be easier to reprint since it doesn't use a distinct keyword.