With scrolling (different format from the Ant Attack to Head over Heels one).
Edit: and Crystal Castles a few years.
Graphics will be what medium and artist allow; in that phase the implementation of depth management in projection was especially impactful.
Wikipedia article: https://en.wikipedia.org/wiki/Isometric_video_game_graphics
[1] https://www.eurogamer.net/the-classic-8-bit-isometric-games-...
(Oh, and the title always made me wonder if it was a Tears for Fears collab, which seemed like such a rad idea at the time)
As others pointed out Zaxxon and Marble Madness came first, but neither allowed the same sort of interaction with the environment (changing depth and moving other blocks around).
Seeing Knight Lore, it very clearly must have been the inspiration for Viva Mortis. How cool. Thanks for sharing.