Bite Down on Crime
As an additional cost to cast this spell, you may collect evidence 6. This spell costs 
less to cast if evidence was collected. (To collect evidence 6, exile cards with total mana value 6 or greater from your graveyard.)
Target creature you control gets +2/+0 until end of turn. It deals damage equal to its power to target creature you don't control.
Illustrated by Mike Bierek
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Once you've announced that you're casting a spell, players can't take actions until you've finished doing so. Notably, opponents can't try to remove cards from your graveyard to stop you from collecting evidence.
If either target is an illegal target as Bite Down on Crime tries to resolve, the creature you control won't deal damage.
If you can't exile enough cards to meet or exceed the required mana value, you can't choose to collect evidence at all.
