Zaxara, the Exemplary
Legendary Creature — Nightmare Hydra
Deathtouch
: Add two mana of any one color.
Whenever you cast a spell with 
in its mana cost, create a 0/0 green Hydra creature token, then put X +1/+1 counters on it.
Simon Dominic
Commander 2020 (C20)
• #20Rulings
The Hydra token enters the battlefield as a 0/0 creature. Any abilities that modify or trigger on this event apply. After the token is on the battlefield but before any player can take actions, +1/+1 counters are put onto the token.
(wotc • 2020-04-17)
If the spell you cast has {X}{X} in its mana cost, the token gets only X counters, not twice X.
(wotc • 2020-04-17)
If X is 0, the 0/0 Hydra token will die immediately after the ability's done resolving unless something else is raising its toughness.
(wotc • 2020-04-17)
The value of X in Zaxara's last ability is the value of X of the spell you cast.
(wotc • 2020-04-17)
If an effect, such as that of Parallel Lives, causes Zaxara's ability to create multiple Hydra tokens, they each receive X +1/+1 counters.
(wotc • 2020-04-17)
Rulings
The Hydra token enters the battlefield as a 0/0 creature. Any abilities that modify or trigger on this event apply. After the token is on the battlefield but before any player can take actions, +1/+1 counters are put onto the token.
(wotc • 2020-04-17)
If the spell you cast has {X}{X} in its mana cost, the token gets only X counters, not twice X.
(wotc • 2020-04-17)
If X is 0, the 0/0 Hydra token will die immediately after the ability's done resolving unless something else is raising its toughness.
(wotc • 2020-04-17)
The value of X in Zaxara's last ability is the value of X of the spell you cast.
(wotc • 2020-04-17)
If an effect, such as that of Parallel Lives, causes Zaxara's ability to create multiple Hydra tokens, they each receive X +1/+1 counters.
(wotc • 2020-04-17)