Erico: Your only real options for Cold on a Ki Focus are to use Cold Fury Ki Focus with some sort of second wind op (which you need to be dwarf for) or Hailstorm Ki Focus (which is +2 and only 2 rounds of Cold damage). That being said you don't have a lot of reasons to use Ki Focus for turning your attacks cold. And, generally, you shouldn't because casting through a weapliment means you can slap a Siberys Shard of Merciless Cold onto it for an untyped permanent damage bonus. Since you are implement based you have to use Frost Dagger over Frost Brand Dagger, but both are really good. Going with dagger also lets you pick up Accurate Dagger as a feat to give you a +1 to hit and Nimble Blade for an extra +1 to hit when you have Combat Advantage. If you don't go with the cold theme and are just trying to get more damage, Goblin Totem is a good and easy way to go about it as is Staff of Ruin which will often do the same thing but slightly more expensive (and Staff Expertise gives you permanent reach on your MBA which is pretty cool). In short if you really want cold, Frost Dagger is the best way to go about it (and pay to slap a Shard on it). If you do you will also want to take Nimble Blade for an extra +1 to hit with Combat Advantage. If you want reach and some cool tricks, go with Goblin Totem or Staff of Ruin. Either way you want to also spend a feat on Superior Implement Training to pick up an accurate version of those implements to "cast" through and you want to adjust your free expertise to follow suit (Light Blade Expertise specifies weapon attacks sadly, but Staff Expertise is your friend).