Issued (inverted) with: Doom of the green planet / Emil Petaja.
Cover art for Star quest by Gray Morrow. Cover art for Doom of the green planet by Jerome Podwil. Interior art for both titles by Jack Gaughan. Source: ISFDB.org website.
Internet speculative fiction database 10600
Star Quest: In a universe that had been ravaged by a thousand years of interplanetary warfare between the star-shattering Romaghins and the equally voracious Setessins, there seemed now but one thing that might bring the destruction to an end. That would be the right catalyst in the hands of the right people.
Doom of the Green Planet: Save a world and it's yours to protect forever. Such was the geasa Diarmid Patrick O'Dowd, ex-starman. He had himself called down the destruction on the Green Planet by destroying its Creator and undermining its guiding Song. Now he must shield it from the aspirations of the next star-wanderer to set down its lush fairy-tale landscape.