If this creature's power is negative as its ability resolves, X is considered to be 0.
Cultivator of Blades
The value of X is determined as Cultivator of Blades's last ability resolves. It won't change later, even if its power changes. If Cultivator of Blades is no longer on the battlefield, use its power as it last existed on the battlefield to determine the value of X.
If you can't put +1/+1 counters on the creature for any reason as fabricate resolves (for instance, if it's no longer on the battlefield), you just create Servo tokens.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Josu Hernaiz
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
