Breaks off stalactites, holds them and then drops them on Lyleks

Drawing on the Force as he ran, he gestured at the ceiling and took hold of several large chunks of crystal stalactites. He rocked them loose with his power, then let them dangle there, waiting for the vibration of the passing horde to cause them to fall.

The tunnel wound left and right as they descended, but Vader saw no side tunnels. Just the single tube continuing to burrow into Ryloth’s crust.

From behind came the boom of falling rock—the crystals Vader had loosened—and the squeals of crushed lyleks. Yet still they came, the horde seemingly unbreakable. And they were still closing.

- Lords of the Sith, Chapter Fourteen, Page 340