The copy on the back of the Demons of Topaz inlay says:
Ozzy, lone and intrepid space traveller and keen exponent of the deadly Sonic Triang explores the seemingly endless depths of the dreaded asteroid, Topaz, searching for the seven jewels he needs to re-energise his ageing spacecraft. But can he survive a confrontation with the Demon Guardians - who slowly awaken to avenge the destruction of the Sacred Crystals!
Demons of Topaz was available in a standard cassette case and was the very first Firebird Gold release. The gold printing on the inlay was changed to yellow for future Gold releases (after Topaz and Buggy Blast), presumably because it was easier and cheaper to reproduce.
Apart from a full page colour advert, there were also double-sided full colour posters that were sent out to shops to put in their shop windows.