My version of Triple Frost Rune Death Knight seeks to draw and copy your Frost spells, stall with freeze effects, then burst your opponent down. There are also some more tempo, board-based versions, but I prefer the combo style presented here. If Lady Deathwhisper copies a good combination of Horn of Winter, Howling Blast, Glacial Advance and Frostwyrm's Fury, you can belt out a LOT of damage across a turn or two.