 Sil was designed by Swiss artist H. R. Giger , who also created the creatures in the Alien films . Donaldson thought Giger was the best man for the film after reading his compendium <unk> , and eventually he and Mancuso flew to Switzerland to meet the artist . What attracted Giger was the opportunity to design " a monster in another way — an aesthetic warrior , also sensual and deadly , like the women look in [ his ] paintings . " While Giger opted to stay in Switzerland to take care of his dying mother instead of flying to Los Angeles to accompany production , he built some puppets in his own studio , and later <unk> sketches and <unk> paintings as production went through . The practical models were made by Steve Johnson and his company XFX , which had already worked with Giger 's designs in <unk> II . Giger had envisioned more stages of Sil 's transformation , but the film only employed the last one , where she is " transparent outside and black inside — like a glass body but with carbon inside , " with XFX doing the translucent skin based on what they had done for the aliens of The Abyss . Sil 's alien form had both full @-@ body <unk> with <unk> arms , heads and torsos , and a body suit . Richard <unk> 's Boss Film Studios was hired for over 50 shots of computer @-@ generated imagery , which included one of the earliest forms of motion capture effects . Using a two @-@ foot @-@ high ( 60 cm ) electric puppet that had sensors translating its movements to a digital Sil , Boss Films managed to achieve in one day what would have once taken as much as three weeks with practical effects . 
