I intended to make a cheap (1 cost) creature that usually does nothing, but occasionally distracts the opponent or infects with poison which the mosquito happened to be carrying. This is just a mosquito, not a dangerous, large, or poisonous creature.
The rules state (under Aegis in code): Attacks cannot be reduced below 1 die.
I don't think this means an attack cannot start with 0 dice. As clarification on my card idea, the attack indicates "no damage". You cannot Bear Strength the mosquito and expect more out of it.