Blue is so good because blue doesn't care what color you play. Counterspells are absolute : no matter what it is, it doesn't come to existence. And the variety of counterspells available is dreamy.
Counterspell : Always perfect in any kind of hand. That's OP.
Cryptic Command : One of the best blue cards ever printed, absolutely gorgeous. A counterspell that replaces itslef. Kefnet has it, Kefnet loves it. The other mods are far from the by-the-way side, allowing a tempo strategy that goes perfectly well with the ticking clock of death that is Kefnet. You need only 5 turns to win, and this card brings you one turn, by itslef, in every situation.
Daze: though it is not a hard counter, it's always unpredictable and keeps my hand full, something that Kefnet appreciates a lot.
Desertion : a little expensive but sooo funny to play, this card will wreck havoc in your opponents' moral. So many artifacts are incredibly strong in commander, and the power to counter-steal the other players' commanders is the bitchiest thing. In any situation, it is still a true counterspell, which is welcomed.
Disallow : probably the best 3-mana counterspell ever printed. So many possibilities... so much unpredictable power ! Goodbye planeswalker ultimates, goodbye powerful ETB effects... or even casting effects.
Dismiss : another counterspell that replaces itslef. Kefnet likes.
Dissipate : usually a normal true counterspell, the exile effect can still save you from some nasty graveyard users. Better counterspells exist, but this card is pretty fair and keeps your friends friendly.
Dissolve : scrying is a good mechanic, especially when combined with Kefnet's draw power. Nice and fair, this counterspell is a quality tool.
Draining Whelk : in French, a whelk is called "Bulot", and it has a strange taste. Connoisseurs who learn to appreciate this taste, however, are in for a treat, because whelks are easy to find, thick, and the can counterspell the hell out of anything and at the same time give you a potential flying beater. This card is heavy. It is able to reverse the balance of a game all by itself. Combine it with the best abuser of ETB effects Deadeye Navigator and that's it. You're a dick.
Force of Will : best counterspell ever.
Lost in the Mist : Lost in the mist has a super funny flavor to me. The opponent is... actually lost in a mist, and not being able to come out of it makes him lose his mind. "Hey George, you here ? Hey guys ! I'm gonna cast a spell to...fizzle oh shit i tripped on a root! And something fell from my pocket! God this mist is awful...". It's so laughable, in my head.
Mana Leak : One of my favourite counterspells in the game, this card had to be here. A good turn-2 play is not so common in EDH.
Mystic Confluence : a pumped up Cryptic Command, this card is almost as powerful, sometimes even better. I do prefer CC, but this one is like its slighlty slower big brother.
Rewind : extremly efficient counterspell in this deck with this commander, it allows you to at least activate Kefnet's ability to draw, and if not to play another counterspell from your hand. It has never failed to bring enormous value.
Which counterspells i don't want to play, and why Show
Mana Drain is too powerful. I love it, but it's too much. It's plenty unfair for my community.
Mental Misstep : isn't so nice in EDH. Sure it will counter
Sensei's Divining Top and
Sol Ring but i dislike the idea to use this card only to counter some specific targets. I like my countering possibilities to be broad. This is also why i don't want to play
Spell Snare,
Negate,
Essence Scatter and all the "specific" counterspells.
Remand is nice since it replaces itself, but i prefer hard counters.
Daze is really sweet and might get its place somewhere pretty soon, i just need to get the card itself :)
I could also play more counterspells, this strategy would actually be viable, but it would kill the fun of the deck. I really feel that 15 counterspells is the maximum i want to include here to keep the games fun and random, and have other ways to win than - Put Kefnet - Beatdown and counter.