Once you cast a spell using flashback, that spell will be exiled once it leaves the stack, whether it resolves, is countered, or tries to resolve but fails
As a silver-bordered card, Grimlock is not legal in officially-sanctioned events and formats but is fine for casual play, and as such gets a bit silly with its rules
As such, while missing out on a Street Wraith or Cursecatcher might be frustrating, by the numbers, the odds of this happening are fairly high
I love it Type Four with infinite mana but just one spell per turn, barring a free spell with an alternate cost like Force of Will
Snow Villiers While lacking some of the downside of some similar creatures, you also have a capped upside on a middling cost creature without evasion who can be rendered impotent by destruction of other things