Radiant Nightmare

Flying, hexproof, rad-casting (Each radiation counter you pay while casting this spell pays for {1}. If this resolves as a permanent, it enters the battlefield with a radiation counter on it, for each radiation counter you spent to cast it.)
When Radiant Nightmare attacks, you may pay {x}{u}{u/b}{b}. If you do, draw X cards. You get Y radiation counters, where Y is the number of radiation counters on Radiant Nightmare.