Kinertia

You may tap one mana to cast Kinertia.
When you have at least one mana tapped, you
can increase the inertial mass of your body or an
item you can touch. Standing still, one can more
easily withstand the force of a river, or with a
running start, a regular tackle hits like a ram.
Casting Kinertia as you throw an item, called
a Kinertial Launch, allows a stone to hit like a
bowling ball, but this requires spending a mana.