The child version of me is off somewhere crying from this comment
If an Omen spell has one or more targets and all of those targets are illegal when the spell tries to resolve, it won't resolve
Fighter of the Night Man
In terms of fighting fliers, Grappling Sundew, Wall of Tanglecord or Traproot Kami offer a delay, there is a lot of cheap spot removal like Aerial Volley, multiplayer options like Clip Wings, sweepers like Corrosive Gale/Hurricane/Skyreaping, options to turn flying into a downside like Bower Passage/Dense Canopy, utility answers like Crushing Canopy and Crushing Vines, 'total shutdown' effects like Elvish Skysweeper, Scattershot Archer or Gravity Well
Or was it the Star Trek CCG
The effect to make Blood tokens for creature tokens is minor but feeds into its other effects if you have no other way to generate artifacts