Rulings

If the target permanent is an illegal target by the time Repeal tries to resolve, the spell doesn't resolve. You don't draw a card.
If a permanent on the battlefield has {X} in its mana cost, X is considered to be 0.
The mana value of a token that isn't a copy of another object is 0. A token that is a copy of another object has the same mana cost as that object.