The twin worlds of Canyroth & Lupinator were once vibrant and full of life, hosting dense tropical rainforests, sweeping savannahs, and mist-shrouded mountain ranges. Their unique opposed orbits around a main phase red giant star, however, damned the two worlds to being the staging grounds for one of the most cataclysmic events in multiverse history: the Blood Tide. Vile priests of Yeenoghu raised cyclopean temples to their savage deity on Canyroth and Lupinator, and in a dark ritual that legend says involved the simultaneous sacrifice of nearly 10 million prisoners and willing cultists alike, collapsed the worlds' star into the planar rift known as “Yeenoghu's Howl”. Direct access to Yeenoghu's realm in the Abyss allowed uncountable legions of slaughter-hungry gnolls to pour out and turn the twin worlds into vast centers of demonic industry, with continent-sized factories and breeding pits powering the mad god's war machine.
While Yeenoghu's Howl was sealed and the Blood Tide defeated in a vast cosmic war, no army dared to land on Canyroth & Lupinator to engage the hordes of gnolls and other terrors stranded there. Instead, the worlds were subjected to a 10 year orbital bombardment that pounded all but the largest structures to dust and rendered their surfaces wastelands of toxic waste and wild magical storms. With their star blotted out, the crusading forces were content to leave the decimated planets in their cold, dark orbits around the tortured knot in space where the Howl had been, believing nothing could ever survive there again.
Still, the multiverse has yet to see a limit to what greed and daring will drive adventurers to try, and the few who have visited Canyroth or Lupinator and come back with some vestige of their lives and sanity intact claim that packs of feral gnolls still roam the ruins, and that some nights, the eerie silence is broken by screams and cultish chanting coming from deep inside the tunnels and catacombs that riddle these supposedly-barren rocks.