Skinner continued by saying: "We wanted to bring them back because they’re wonderful!. In the mix of stories that we were planning for this year it felt as if doing something very bold with a monster that hadn’t been seen for a while would be really cool. Mark is an enormous fan of the Ice Warrior stories and came up with the idea.
The sense of a monster of that scale and that size trapped in a really small, contained environment such as a submarine was a really brilliant story to be able to tell. And obviously we’ve had a huge amount of fun going back to the traditional designs and recreating them, bringing the Ice Warriors back to life again.
They were such a beautiful original design, and are genuinely really scary in terms of what they look like as they’re coming towards you in that armour. Letting a huge Ice Warrior loose at the heart of a classic Hunt For Red October style submarine movie was exactly the kind of story that the Doctor should get mixed up in.
They’ve got really scary voices as well. I spent quite a lot of time on set trying to hiss like an Ice Warrior…”

You can see the SFX article here.