Gemma Arterton says she found killing people on-screen a challenge.
The Hansel And Gretel: Witch Hunters actress, who portrays ruthless vampire Clara in Byzantium, admitted the blood-sucking scenes take quite a bit of work to get right.
"It's quite hard doing stuff like that technically, because there's a lot of rigs you have to set up with pumps and blood," she said.
"The timing has to be right, it's very messy and sometimes you're not quite in the flow with it because you have to reset and all of those things. But when you get it right, you feel like 'yes' (a sense of achievement)."
Gemma - who stars alongside Saoirse Ronan as her screen daughter Eleanor - revealed murdering Tom Hollander's character was satisfying.
"Killing Tom Hollander was particularly fun. I think he could tell. He said, 'I think you're enjoying this too much' and I said, 'Yeah. I don't want it to end. It's brilliant'," she said.
"I had this rig going all the way up my arm through my finger and into my thumb so when I stabbed him and pulled out, all the blood would spray out. But it worked perfectly and afterwards, we were very pleased."
The 27-year-old also said she enjoys concocting ways for her victims to meet their end.
"On the page, it just says, 'and she kills him'. You don't know how, so that's where I got really creative... and we worked on techniques and what I could do. That was fun," she added.
:: Byzantium opens in cinemas tomorrow (May 31).