Rulings
The target player is chosen as you announce Void, but the number isn’t chosen until it’s resolving. No player may choose to take actions between you choosing a number and the rest of Void’s effects.
(wotc • 2016-06-08)
You can choose 0. Artifact lands and most tokens have mana values of 0, for example.
(wotc • 2016-06-08)
Rulings
The target player is chosen as you announce Void, but the number isn’t chosen until it’s resolving. No player may choose to take actions between you choosing a number and the rest of Void’s effects.
(wotc • 2016-06-08)
You can choose 0. Artifact lands and most tokens have mana values of 0, for example.
(wotc • 2016-06-08)