Even without a power cost 0 character card in your hand, you set up the game by placing a character card with a power cost of 1 or more, an enchant card or an area enchant card face down in the battle zone.
If you set an enchant or area enchant card, it goes to the power charger or abyss "immediately" when the game starts, and its effect can't be used even if its power cost is 0. Your attack this turn (turn 1) counts as 0, so you take your opponent's attack as it is.