The Altar at Asconel — John Brunner

Whether or not he had wanted to turn back at the last minute, he couldn't have - the wave of dirty, hungry people carried him helplessly along in their fervour reach the temple. Like dope addicts, he told himself, they don't even care about themselves, only about the thing that is inside the temple!

He remembered the day ten years ago when his older brother had been made a Warden of Asconel, a prosperous and happy planet, and he and his other brothers had left in the interests of their people. Now they returned to a world where a fanatical cult had usurped the Warden's chair, and men and women were offering themselves up as human sacrifices to Belizuek - whoever or whatever that being from beyond the galaxy was . . .

I'll find out, he told himself grimly, when I enter these doors . . .

(First published 1965)