This set is affected by the earth skill. Until very recently, I ignored the 10-pointer message, but thanks to Exoth I have stumbled upon it at last. He also got a tm from it too, definitely confirming the suspicions.
All results have been confirmed for all levels.
1) 10-pointer: fresh earth. "Erratic Mechanic Exoth hits the cue ball with his dark brown oak staff, sending it towards the beige ball. / The two balls collide and the beige ball rolls into a corner pocket leaving behind only the smell of freshly dug earth."
2) 15-pointer: rock. "Krotos taps the cue ball with his Nonsense, sending it rolling towards the brown ball. / As the balls collide, the brown ball turns into a perfectly spherical rock and rolls into a corner pocket."
3) 20-pointer: zombie hands ("You hit the cue ball with your blackened iron staff. / Suddenly, a row of tiny, and rather zombie-like, hands rip through the surface of the table. / The cue ball is picked up and passed from hand to hand until it is dropped on the beige ball which rolls into a corner pocket.") and mountains ("You hold your blackened iron staff horizontally above the table and mutter a few words. / The surface of the table is briefly transformed into a miniature mountain range and the cue ball rolls down a mountain, hits the beige ball causing it to zoom into a corner pocket.")
4) 30-pointer: earthquake. "You hold your blackened iron staff aloft and bring it straight down, striking the floor with it dramatically. / A minor yet highly localised earthquake shakes the room, causing the table to rock and the cue ball to knock the brown ball into a side pocket