The space wolf flyers were the new shiny to come out in the latest codex, and I wanted one.
Pixma - Waves
Much like my Skitarri were my 2015 birthday present to myself, the Stormfang was my 2015 Christmas present to myself with some bonus money. (This breaks my self-imposed rule of no new 40k purchases until I've finished painting the last one but - meh! I wanted the shiny and it was Christmas).