Except for the concluding bluescreen shots in Helsinki, Dark Floors was lensed entirely in a former factory for Nokia components in provincial Oulu, otherwise the home town of a children's film festival, this year's Nordisk Panorama and the annual Air Guitar World Championships.
Corridors were set up to represent a five-floor hospital - 'each floor scarier than the other,' said Riski. The film stars the monster group of Mr Lordi (Tomi Putaansuu), Amen the Unstoppable Mummy, Awa the Vampire Countess, Ox the Hellbull and Kita the Alien Manbeast.
In an otherwise mainly UK cast - the film is shot in English - 12-year-old Skye Deva Bennett plays her first lead as Sarah, a hospitalised autistic girl, with supporting cast including Dominique McElligott, Noah Huntley, Ronald Pickup, Philip Bretherton, Leon Herbert and William Hope.
From an idea by Mr Lordi-Putaansuu, who scripted with Veli-Pekka Hanninen, Dark Floors follows Sarah's father breaking into the hospital to take her home. Suddenly creatures from a dark world start an attack, leaving mutilated bodies all over. Survival rests solely on the little girl.
Both Putaansuu and Riski grew up in the Finnish town of Rovaniemi - where a square is now named after Lordi - and they started to make horror movies when they were 15. Putaansuu went to film school in Torni and became a director, graduating with a Lordi music video.
'One day I hope to make my own film, but right now I am too busy with the band - we just completed the Ozzfest Tour in the US. Pete and I are soul mates, we know what the other thinks. He has made all our videos, and I trust him completely,' Putaansuu added.
Dark Floors producer Markus Selin of Solar Films has for the last four years delivered the top local blockbuster on the Finnish charts - and is leading this year by V2 Dead Angel.
Dark Floors will be released domestically on Feb 8. Nordisk handles foreign sales.