Stormbringer ll: Lightning Nest

The heroes of THE RAT AND THE RAVEN have returned to the University, but they are restless. They don't fit in any more. Swart is told dreadful news by his father, and at the same time a petitioner comes on foot from far away, begging the wise people of the University for help against an enemy who wields lightning as a weapon. So it is time for Bran to gather his group again: the giant Mill the Hill, the dangerous twins Aethelflaed, the cowardly Dismas who can open any lock if he is scared enough, and Bran's beautiful, strange lover Scathe, a transmitting empath.
They must find the Lightning Nest - a Tesla construct, and disable it. Harder things will also be asked of them before the end.