By 1986 the ZX Spectrum was awash with isometric action/adventures games. After the success of Ultimate Play The Game‘s Knight Lore, everyone was trying to make and release them.
Looking back now I would have to say that many of the so-called “clones” were actually very good, although few were outstanding.
Piranha‘s Nosferatu the Vampyre was one of the few outstanding ones, it having been created by Spectrum veteran game design team Design Design, and it also being an interesting take on the classic tale of vampirism written by Bram Stoker (actually this game being based on the 1979 film starring Klaus Kinski).
