I would suggest that you remember she is old because some of her enemies are dead. - C. J. Cherryh

Brains and sex fight each other to control your life, and thank God brains get a head start before sex comes along.

"Why?" Lee asked after a moment. "Why do you make such a bargain?"
"For the going," said Ras very softly. "The going itself is our hire. Use us wisely, human sen'en, for we are a sharp sword, to part the Dark for you. So we did for the regul, I have heard, giving them many worlds. And when we have gone far enough, and the tether strains...bid us good-bye, and be wiser that the regul. We are the Face that Looks Outward. We are makers of paths, walkers on the wind; and the going itself...is the hire for which we have always served."
Boaz pressed her lips together, thinking for one cold moment on the dead worlds, about which human councils would have to know, the course of mri homeworlds, destroyed beneath the mri in fear, fears which had to come to former wielders of the Sword: dread that mri might serve others, one's near neighbors. Fear. Fear had killed the worlds between.
To use the mri, one had to play the Game, to cast them from the hand and let them go.

The world was full of life, more life than they could hold back with guns or fences; it came into the town at night; it seduced the children and year by year crept closer.