If I have multiple Constantine characters fielded, do I get to name multiple characters?
While Constantine is active, before your opponent’s Clear and Draw Step, you may name a character. If that character is fielded this turn, ignore its text until end of turn and it cannot attack this turn.
So if I have 2 Constantine Hellblazers, I can name black widow and hulk?
No. “While active” effects take place only once regardless of how many copies of that die are in the field.
The relevant text from the rulebook is as follows:
DC Dice Masters: Justice League Rulebook Page 21:
When game text says, “While ___ is active,” that means “When one or more of this card’s dice are in the field.” In other words, when dice of that character have been fielded, the effect on the card takes place. It takes place only once, no matter how many copies of that die are fielded.
-The Dice Masters Rules Team