Two days ago, Jonny broke your arm, and Xander healed it.
The cut healed itself in seconds.
She started to saw at them with the knife. The wood was thick and wet. She shifted closer, gasping when the root healed the cuts she'd just made. Furious at the latest trick from the Immortal underworld, Katie sawed furiously at the root, until her arm ached. She'd barely made a dent when she switched arms.